EP0595060B1 - Internal combustion engine valve drive - Google Patents

Internal combustion engine valve drive Download PDF

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Publication number
EP0595060B1
EP0595060B1 EP93115881A EP93115881A EP0595060B1 EP 0595060 B1 EP0595060 B1 EP 0595060B1 EP 93115881 A EP93115881 A EP 93115881A EP 93115881 A EP93115881 A EP 93115881A EP 0595060 B1 EP0595060 B1 EP 0595060B1
Authority
EP
European Patent Office
Prior art keywords
drive according
camshaft
cam
transmission member
sliding cam
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
Application number
EP93115881A
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German (de)
French (fr)
Other versions
EP0595060A1 (en
Inventor
Winfried Krebs
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dr Ing HCF Porsche AG
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Dr Ing HCF Porsche AG
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Publication date
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Publication of EP0595060A1 publication Critical patent/EP0595060A1/en
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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
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/18—Rocking arms or levers
    • F01L1/185—Overhead end-pivot rocking arms
    • 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
    • F01L1/26—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder
    • F01L1/267—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of two or more valves operated simultaneously by same transmitting-gear; peculiar to machines or engines with more than two lift-valves per cylinder with means for varying the timing or the lift of the valves
    • 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
    • F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
    • F01L13/0036—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
    • 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
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/14—Tappets; Push rods
    • F01L1/143—Tappets; Push rods for use with overhead camshafts
    • 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
    • F01L1/02—Valve drive
    • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
    • F01L1/047—Camshafts
    • F01L2001/0475—Hollow camshafts
    • 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
    • F01L1/02—Valve drive
    • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
    • F01L1/047—Camshafts
    • F01L2001/0476—Camshaft bearings
    • 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
    • F01L2305/00—Valve arrangements comprising rollers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/21—Elements
    • Y10T74/2101—Cams
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/21—Elements
    • Y10T74/2101—Cams
    • Y10T74/2102—Adjustable

Definitions

  • the invention relates to a valve drive for an internal combustion engine according to the preamble of claim 1.
  • DE-OS 20 37 705 discloses a generic valve drive with a hydraulically axially displaceable camshaft on which fixed cams with two different elevation curves are arranged.
  • gas exchange valves with a larger valve stroke are actuated in one end position of the camshaft, while when the oil pressure is switched off the camshaft is spring-loaded and moved to a second end position, the valves are actuated with a smaller valve stroke.
  • the disadvantage here is the simultaneous axial displacement of all cams.
  • the angular offset of the cams to one another means that no position of the camshaft can be found in which all the cams run simultaneously on their base circle, as would be necessary for an axial displacement.
  • the cams assigned to the exhaust valves are also displaced.
  • a valve train with axially spirally displaceable and rotatable cams on the camshaft is known.
  • the cams are held on the camshaft by means of a form fit by means of a spiral thread.
  • Axially displaceable shafts run parallel to the camshaft, which engage the cams from the outside by means of drivers and rotate them relative to the camshaft in order to set optimal timing times.
  • the cams actuate gas exchange valves with the interposition of transmission elements designed as rocker arms. This arrangement takes up a considerable amount of space due to the axially displaceable shafts, is heavy and susceptible to wear due to the sliding contact between rotating cams and drivers.
  • a spiral toothing on the camshaft is expensive to manufacture.
  • valve drive with the features of the main claim has the advantage that gas exchange valves of all cylinders in a row of cylinders can be operated with this valve drive.
  • the sliding cams are axially biased against the stops as long as they run on this stop with their sections of their end face limited by the elevation curves. If the base circle of each slide cam reaches the transmission element, the slide cams are displaced and run with their elevation curve on the transmission element.
  • This valve drive can be used, for example, in the case of directly actuated valves, it being possible for the transmission element to be designed as a bucket tappet provided with hydraulic valve clearance compensation.
  • the valve drive can be used with valve drives provided with levers.
  • the transmission element is designed as a rocker arm, rocker arm or the like.
  • the sliding cams can be provided with two elevation curves, the portion abutting the stop being formed between the two elevation curves.
  • the different elevation curves running on the transmission element can have an angular offset to one another, so that there is a phase shift.
  • This phase shift can be used together with the variation of the valve lift or instead of this.
  • a valve drive of an internal combustion engine has a camshaft 2 held in bearings 1, which is driven in the usual way by a crankshaft.
  • a non-rotatable cam which is displaceable in a longitudinal direction L and is designed as a sliding cam 3.
  • This sliding cam 3 is displaceable along a guide 4 which positively connects it and the camshaft 2 from a first S1 to a second position S2.
  • the sliding cam 3 actuates two gas exchange valves designed as inlet valves 6 with the interposition of a transmission element 5.
  • a stop 7 is formed between the sliding cam 3 and the transmission element 5.
  • the sliding cam 3 is axially biased with one of its end faces 8.
  • the axial preload is applied either by a compression spring 9 or a hydraulically actuated piston 10.
  • This piston 10 is slidably inserted in a sleeve 11, which in turn is arranged between the bearing 1 and the camshaft 2. Via a central channel 12 of the camshaft 2 and radial bores 13 branching therefrom, the piston 10 is connected to a hydraulic circuit, not shown, which acts on the central channel 12 with pressure oil depending on parameters of the internal combustion engine or keeps it free of oil pressure.
  • a fixed cam 15 is arranged centrally on the camshaft 2 between two sliding cams 3 which can be displaced in relation to one another.
  • a compression spring 9 is supported on this on both sides which hold the slide cams 3 in the first position S1 when the oil pressure is switched off.
  • All cams 3, 15 have a base circle 16 and the fixed cam 15 has a first elevation curve 17, which has a shorter stroke than the second elevation curve 18 of the sliding cams 3.
  • the transmission element 5 has on the sliding cams 3 facing end faces 19 designed as a stepped recess 20 stops 7.
  • valves 6 When the internal combustion engines are operating, the valves 6 are first actuated by the fixed cam 15 according to their elevation curve 17 when the central channel 12 is free of oil pressure.
  • the sliding cam 3 run together with the fixed cam 15 without running onto the transmission element 5, since the clearance 20 provides sufficient clearance for the second elevation curves 18.
  • the pistons 10 press on the other end 8 of the sliding cam 3 facing away from the compression spring 9 and try to move it in the direction of the fixed cam 15. If the slide cams 3 run during the pressure oil connection with a section 21 of their one end face 8 limited by their elevation curve 18 in the recess 20, the slide cams 3 bear positively on the stop 7 due to the hydraulic prestress.
  • two sliding cams 3 which can be displaced in relation to one another each have a first and a second elevation curve 17 and 18.
  • both sliding cams 3 are spring-loaded in the first position S1 and act on the transmission element 5 with the first elevation curves 17.
  • the recess 20 in turn provides sufficient clearance for the elevation curves 18 provided with a larger stroke.
  • the sliding cams 3 are again in contact with the section 21 at the stop 7, before they are moved during their base circle 16 into the second position S2 shown in dashed lines in FIG. 4, in which they press the valves 6 with the second elevation curves 18 act.
  • the third embodiment according to FIG. 5 has a single sliding cam 3 with two elevation curves 17, 18.
  • the sleeve 11 is arranged adjacent to a bearing 1 on the camshaft 2 separately.
  • the transmission element 5 has a roller 22 which evenly distributes the transmitted forces, one side surface 23 of which forms the stop 7 for the section 21. In the first position S1, the roller 22 is in contact with the elevation curve 17, in the second position S2 with the elevation curve 18.
  • Fig. 6 shows the positive connection used in all embodiments between the sliding cam 3 and the camshaft 2 by the guide 4 running in the longitudinal direction L, which is formed, for example, by keys 24 inserted in grooves.
  • a phase shift between the first and second elevation curves can be achieved by these curves relative to one another are arranged offset in angle. This angular offset can also be realized without varying the stroke, so that the valve drive acts as a phase converter.
  • a line 26 shows the congruent main axes of the in-phase elevation curves 17 and 18, while a dashed line 27 shows the main axis of an out-of-phase elevation curve.

Landscapes

  • 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 betrifft einen Ventilantrieb für eine Brennkraftmaschine gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a valve drive for an internal combustion engine according to the preamble of claim 1.

In der DE-OS 20 37 705 ist ein gattungsgemäßer Ventilantrieb mit einer hydraulisch axial verschiebbaren Nockenwelle offenbart, auf der Festnocken mit zwei unterschiedlichen Erhebungskurven angeordnet sind. Bei zugeschaltetem Öldruck werden Gaswechselventile mit größerem Ventilhub in einer Endlage der Nockenwelle betätigt, während bei abgeschaltetem Öldruck die Nockenwelle federbelastet in eine zweite Endlage verschoben die Ventile mit einem geringeren Ventilhub betätigt.
Nachteilig hierbei ist das gleichzeitige axiale Verschieben aller Nocken. Bei einer mehrzylindrigen Brennkraftmaschine läßt sich durch den Winkelversatz der Nocken zueinander keine Stellung der Nockenwelle finden, in der alle Nocken gleichzeitig auf ihrem Grundkreis laufen, wie es zu einer axialen Verschiebung nötig wäre. Zudem werden bei Brennkraftmaschinen mit nur einer Nockenwelle je Zylinderreihe auch die den Auslaßventilen zugeordneten Nocken verschoben.DE-OS 20 37 705 discloses a generic valve drive with a hydraulically axially displaceable camshaft on which fixed cams with two different elevation curves are arranged. When the oil pressure is switched on, gas exchange valves with a larger valve stroke are actuated in one end position of the camshaft, while when the oil pressure is switched off the camshaft is spring-loaded and moved to a second end position, the valves are actuated with a smaller valve stroke.
The disadvantage here is the simultaneous axial displacement of all cams. In the case of a multi-cylinder internal combustion engine, the angular offset of the cams to one another means that no position of the camshaft can be found in which all the cams run simultaneously on their base circle, as would be necessary for an axial displacement. In addition, in internal combustion engines with only one camshaft per row of cylinders, the cams assigned to the exhaust valves are also displaced.

Aus der DE-29 50 656 A1 ist ein Ventiltrieb mit axial spiralförmig auf der Nockenwelle verschieb- und verdrehbaren Nocken bekannt. Die Nocken sind dabei mittels spiralförmiger Gewinde durch Formschluß auf der Nockenwelle gehalten. Parallel zur Nockenwelle verlaufen axial verschiebbare Wellen, welche über Mitnehmer von außen schleifend in die Nocken eingreifen und diese relativ zur Nockenwelle zur Einstellung optimaler Steuerzeiten verdrehen. Die Nocken betätigen unter Zwischenschaltung von als Kipphebel ausgebildeten Übertragungselementen Gaswechselventile. Diese Anordnung beansprucht durch die axial verschiebbaren Wellen einen erheblichen Bauraum, ist schwergewichtig und durch den schleifenden Kontakt zwischen rotierenden Nocken und Mitnehmern verschleißanfällig. Zudem ist eine spiralförmige Verzahnung auf der Nockenwelle fertigungsaufwendig.From DE-29 50 656 A1 a valve train with axially spirally displaceable and rotatable cams on the camshaft is known. The cams are held on the camshaft by means of a form fit by means of a spiral thread. Axially displaceable shafts run parallel to the camshaft, which engage the cams from the outside by means of drivers and rotate them relative to the camshaft in order to set optimal timing times. The cams actuate gas exchange valves with the interposition of transmission elements designed as rocker arms. This arrangement takes up a considerable amount of space due to the axially displaceable shafts, is heavy and susceptible to wear due to the sliding contact between rotating cams and drivers. In addition, a spiral toothing on the camshaft is expensive to manufacture.

Demgegenüber hat der Ventilantrieb mit den Merkmalen des Hauptanspruches den Vorteil, daß Gaswechselventile aller Zylinder einer Zylinderreihe mit diesem Ventilantrieb betätigt werden können. Die Schiebenocken liegen dabei axial vorgespannt so lange an den Anschlägen an, wie sie mit ihren durch die Erhebungskurven begrenzten Abschnitten ihrer Stirnseite auf diesem Anschlag laufen. Erreicht der Grundkreis jeder Schiebenocke das Übertragungselement, so werden die Schiebenocken verschoben und laufen mit ihrer Erhebungskurve auf dem Übertragungselement.
Dieser Ventilantrieb ist z.B. anwendbar bei direkt betätigten Ventilen, wobei das Übertragungselement als ein mit hydraulischem Ventilspielausgleich versehener Tassenstößel ausgebildet sein kann. Desweiteren kann der Ventilantrieb bei mit Hebeln versehenen Ventiltrieben verwendet werden. Hierbei ist das Übertragungselement als Kipphebel, Schwinghebel oder dergleichen ausgebildet.In contrast, the valve drive with the features of the main claim has the advantage that gas exchange valves of all cylinders in a row of cylinders can be operated with this valve drive. The sliding cams are axially biased against the stops as long as they run on this stop with their sections of their end face limited by the elevation curves. If the base circle of each slide cam reaches the transmission element, the slide cams are displaced and run with their elevation curve on the transmission element.
This valve drive can be used, for example, in the case of directly actuated valves, it being possible for the transmission element to be designed as a bucket tappet provided with hydraulic valve clearance compensation. Furthermore, the valve drive can be used with valve drives provided with levers. Here, the transmission element is designed as a rocker arm, rocker arm or the like.

Die Schiebenocken können mit zwei Erhebungskurven versehen sein, wobei der am Anschlag anliegende Abschnitt zwischen den beiden Erhebungskurven ausgebildet ist.The sliding cams can be provided with two elevation curves, the portion abutting the stop being formed between the two elevation curves.

Die verschiedenen auf dem Übertragungselement laufenden Erhebungskurven können einen Winkelversatz zueinander aufweisen, so daß sich eine Phasenverschiebung ergibt. Diese Phasenverschiebung kann gemeinsam mit der Variation des Ventilhubes oder anstelle dieser verwendet werden.The different elevation curves running on the transmission element can have an angular offset to one another, so that there is a phase shift. This phase shift can be used together with the variation of the valve lift or instead of this.

Anhand einer Zeichnung wird nachfolgend ein Ausführungsbeispiel der Erfindung näher erläutert.An exemplary embodiment of the invention is explained in more detail below with reference to a drawing.

Es zeigen:

Fig. 1
einen Längsschnitt einer ersten Ausführungsform der Erfindung mit Schiebenocken in einer ersten Stellung,
Fig. 2
ein Schnitt ähnlich Fig. 1 mit Schiebenocken in einer zweiten Stellung,
Fig. 3
ein Schnitt entlang der Linie III-III gemäß Fig. 2,
Fig. 4
ein Längsschnitt einer zweiten Ausführungsform,
Fig. 5
ein Längsschnitt einer dritten Ausführungsform und
Fig. 6
ein Schnitt entlang der Linie VI-VI gemäß Fig. 5.
Show it:
Fig. 1
2 shows a longitudinal section of a first embodiment of the invention with sliding cams in a first position,
Fig. 2
2 shows a section similar to FIG. 1 with sliding cams in a second position,
Fig. 3
3 shows a section along the line III-III according to FIG. 2,
Fig. 4
2 shows a longitudinal section of a second embodiment,
Fig. 5
a longitudinal section of a third embodiment and
Fig. 6
a section along the line VI-VI of FIG .. 5

Ein Ventilantrieb einer nicht gezeigten Brennkraftmaschine weist eine in Lagern 1 gehaltene Nockenwelle 2 auf, welche in üblicher Weise von einer Kurbelwelle angetrieben wird.
Auf der Nockenwelle 2 ist eine drehfeste, relativ zu ihr in eine Längsrichtung L verschiebbare, als Schiebenocke 3 ausgebildete Nocke angeordnet. Diese Schiebenocke 3 ist dabei längs einer sie und die Nockenwelle 2 formschlüssig verbindenden Führung 4 von einer ersten S1 in eine zweite Stellung S2 verschiebbar.A valve drive of an internal combustion engine, not shown, has a camshaft 2 held in bearings 1, which is driven in the usual way by a crankshaft.
Arranged on the camshaft 2 is a non-rotatable cam which is displaceable in a longitudinal direction L and is designed as a sliding cam 3. This sliding cam 3 is displaceable along a guide 4 which positively connects it and the camshaft 2 from a first S1 to a second position S2.

Die Schiebenocke 3 betätigt unter Zwischenschaltung eines Übertragungselementes 5 zwei als Einlaßventile 6 ausgebildete Gaswechselventile.
Zwischen Schiebenocke 3 und Übertragungselement 5 ist ein Anschlag 7 ausgebildet. An diesem Anschlag 7 liegt die Schiebenocke 3 axial vorgespannt mit einer ihrer Stirnseiten 8 an. Die axiale Vorspannung wird dabei entweder durch eine Druckfeder 9 oder einen hydraulisch beaufschlagten Kolben 10 aufgebracht.The sliding cam 3 actuates two gas exchange valves designed as inlet valves 6 with the interposition of a transmission element 5.
A stop 7 is formed between the sliding cam 3 and the transmission element 5. At this stop 7, the sliding cam 3 is axially biased with one of its end faces 8. The axial preload is applied either by a compression spring 9 or a hydraulically actuated piston 10.

Dieser Kolben 10 ist verschieblich in einer Hülse 11 eingesetzt,welche wiederum zwischen Lager 1 und Nockenwelle 2 angeordnet ist. Über einen Zentralkanal 12 der Nockenwelle 2 und davon abzweigende radiale Bohrungen 13 ist der Kolben 10 an einen nicht gezeigten Hydraulikkreis angeschlossen, welcher den Zentralkanal 12 in Abhängigkeit von Parametern der Brennkraftmaschine mit Drucköl beaufschlagt oder ihn öldruckfrei hält.This piston 10 is slidably inserted in a sleeve 11, which in turn is arranged between the bearing 1 and the camshaft 2. Via a central channel 12 of the camshaft 2 and radial bores 13 branching therefrom, the piston 10 is connected to a hydraulic circuit, not shown, which acts on the central channel 12 with pressure oil depending on parameters of the internal combustion engine or keeps it free of oil pressure.

In einer ersten Ausführungsform der Erfindung gemäß Fig. 1 ist mittig zwischen zwei entgegengesetzt zueinander verschiebbaren Schiebenocken 3 eine Festnocke 15 auf der Nockenwelle 2 angeordnet. An dieser stützt sich beidseitig eine Druckfeder 9 ab, welche die Schiebenocken 3 bei abgeschaltetem Öldruck in der ersten Stellung S1 halten.In a first embodiment of the invention according to FIG. 1, a fixed cam 15 is arranged centrally on the camshaft 2 between two sliding cams 3 which can be displaced in relation to one another. A compression spring 9 is supported on this on both sides which hold the slide cams 3 in the first position S1 when the oil pressure is switched off.

Alle Nocken 3, 15 weisen einen Grundkreis 16 auf und die Festnocke 15 eine erste Erhebungskurve 17, welche einen geringeren Hub aufweist als zweite Erhebungskurve 18 der Schiebenocken 3.
Das Übertragungselement 5 weist an den Schiebenocken 3 zugewandten Stirnflächen 19 als gestufte Ausnehmung 20 ausgebildete Anschläge 7 auf.All cams 3, 15 have a base circle 16 and the fixed cam 15 has a first elevation curve 17, which has a shorter stroke than the second elevation curve 18 of the sliding cams 3.
The transmission element 5 has on the sliding cams 3 facing end faces 19 designed as a stepped recess 20 stops 7.

Im Betrieb der Brennkraftmaschinen werden zunächst bei öldruckfreiem Zentralkanal 12 die Ventile 6 von der Festnocke 15 gemäß ihrer Erhebungskurve 17 betätigt. Die Schiebenocken 3 laufen gemeinsam mit der Festnocke 15 um ohne auf das Übertragungselement 5 aufzulaufen, da durch die Ausnehmung 20 ein für die zweiten Erhebungskurven 18 ausreichender Freigang gegeben ist.
Bei zugeschaltetem Drucköl drücken die Kolben 10 auf die den Druckfeder 9 abgewandte, andere Stirnseite 8 der Schiebenocke 3 und versuchen diese in Richtung auf die Festnocke 15 zu verschieben. Laufen die Schiebenocken 3 während der Druckölzuschaltung mit einem durch ihre Erhebungskurve 18 begrenzten Abschnitt 21 ihrer einen Stirnseite 8 in der Ausnehmung 20, so liegen die Schiebenocken 3 durch die hydraulische Vorspannung formschlüssig an dem Anschlag 7 an. Verläßt bei weiterer Drehung der Schiebenocken 3 der Abschnitt 21 den Bereich der Ausnehmung 20, werden diese auf dem Grundkreis 16 laufend in die in Fig. 2 gezeigte zweite Stellung S2 verschoben. Die Einlaßventile 6 werden nunmehr gemäß der zweiten Erhebungskurve 18 betätigt.
Vorteilhafterweise können somit während einer einzigen Umdrehung der Nockenwelle 2 alle Schiebenocken 3 einer Reihe von Zylindern der Brennkraftmaschine betätigt werden. Die während der Druckölzuschaltung auf ihrem Grundkreis 16 laufenden Schiebenocken 3 werden sofort in die zweite Stellung S2 verschoben, während alle anderen kurzzeitig an dem Anschlag 7 anliegen, bevor sie in diese Stellung S2 verschoben werden. Eine separate hydraulische Ansteuerung aller einzelnen Zylinder der Brennkraftmaschine kann entfallen.When the internal combustion engines are operating, the valves 6 are first actuated by the fixed cam 15 according to their elevation curve 17 when the central channel 12 is free of oil pressure. The sliding cam 3 run together with the fixed cam 15 without running onto the transmission element 5, since the clearance 20 provides sufficient clearance for the second elevation curves 18.
When the pressure oil is switched on, the pistons 10 press on the other end 8 of the sliding cam 3 facing away from the compression spring 9 and try to move it in the direction of the fixed cam 15. If the slide cams 3 run during the pressure oil connection with a section 21 of their one end face 8 limited by their elevation curve 18 in the recess 20, the slide cams 3 bear positively on the stop 7 due to the hydraulic prestress. If the section 21 leaves the area of the recess 20 upon further rotation of the sliding cams 3, these are continuously shifted on the base circle 16 into the second position S2 shown in FIG. 2. The inlet valves 6 are now operated according to the second elevation curve 18.
Advantageously, all sliding cams 3 of a row of cylinders of the internal combustion engine can thus be actuated during a single revolution of the camshaft 2. The sliding cams 3 running on their base circle 16 during the pressure oil connection are immediately shifted into the second position S2, while all others are briefly in contact with the stop 7 before they are shifted into this position S2. A separate hydraulic control of all individual cylinders of the internal combustion engine can be omitted.

Gemäß einer in Fig. 4 gezeigten zweiten Ausführungsform der Erfindung weisen zwei entgegengesetzt zueinander verschiebbare Schiebenocken 3 jeweils eine erste und eine zweite Erhebungskurve 17 und 18 auf. Bei abgeschaltetem Öldruck stehen beide Schiebenocken 3 federbelastet in der ersten Stellung S1 und wirken dabei mit den ersten Erhebungskurven 17 auf das Übertragungselement 5. Die Ausnehmung 20 stellt wiederum einen ausreichenden Freigang für die mit größerem Hub versehenen Erhebungskurven 18 bereit.
Bei zugeschaltetem Drucköl liegen die Schiebenocken 3 zunächst wieder mit dem Abschnitt 21 an dem Anschlag 7, bevor sie während ihres Grundkreises 16 in die in Fig. 4 gestrichelt dargestellte zweite Stellung S2 verschoben werden, in welcher sie mit den zweiten Erhebungskurven 18 auf die Ventile 6 einwirken.According to a second embodiment of the invention shown in FIG. 4, two sliding cams 3 which can be displaced in relation to one another each have a first and a second elevation curve 17 and 18. When the oil pressure is switched off, both sliding cams 3 are spring-loaded in the first position S1 and act on the transmission element 5 with the first elevation curves 17. The recess 20 in turn provides sufficient clearance for the elevation curves 18 provided with a larger stroke.
When the pressure oil is switched on, the sliding cams 3 are again in contact with the section 21 at the stop 7, before they are moved during their base circle 16 into the second position S2 shown in dashed lines in FIG. 4, in which they press the valves 6 with the second elevation curves 18 act.

Die dritte Ausführungsform gemäß Fig. 5 weist eine einzige Schiebenocke 3 mit zwei Erhebungskurven 17, 18 auf. Die Hülse 11 ist benachbart eines Lagers 1 separat auf der Nockenwelle 2 angeordnet.
Das Übertragungselement 5 weist eine die übertragenen Kräfte gleichmäßig verteilende Rolle 22 auf, deren eine Seitenfläche 23 den Anschlag 7 für den Abschnitt 21 bildet. In der ersten Stellung S1 steht die Rolle 22 mit der Erhebungskurve 17, in der zweiten Stellung S2 mit der Erhebungskurve 18 in Kontakt.The third embodiment according to FIG. 5 has a single sliding cam 3 with two elevation curves 17, 18. The sleeve 11 is arranged adjacent to a bearing 1 on the camshaft 2 separately.
The transmission element 5 has a roller 22 which evenly distributes the transmitted forces, one side surface 23 of which forms the stop 7 for the section 21. In the first position S1, the roller 22 is in contact with the elevation curve 17, in the second position S2 with the elevation curve 18.

Fig. 6 zeigt die bei allen Ausführungsformen verwendete formschlüssige Verbindung zwischen Schiebenocken 3 und Nockenwelle 2 durch die in Längsrichtung L verlaufende Führung 4, welche beispielsweise durch in Nuten eingelegte Paßfedern 24 gebildet wird.Fig. 6 shows the positive connection used in all embodiments between the sliding cam 3 and the camshaft 2 by the guide 4 running in the longitudinal direction L, which is formed, for example, by keys 24 inserted in grooves.

Zusätzlich zu der durch den erfindungsgemäßen Ventilantrieb möglichen Variationen des Ventilhubes kann eine Phasenverschiebung zwischen den ersten und zweiten Erhebungskurven erzielt werden, in dem diese Kurven zueinander winkelversetzt angeordnet sind. Dieser Winkelversatz kann auch ohne Variation des Hubes realisiert sein, so daß der Ventilantrieb als Phasenwandler wirkt. In Fig. 6 zeigt eine Linie 26 die deckungsgleichen Hauptachsen der phasengleichen Erhebungskurven 17 und 18, während eine gestrichelte Linie 27 die Hauptachse einer phasenverschobenen Erhebungskurve zeigt.In addition to the variations of the valve lift possible by the valve drive according to the invention, a phase shift between the first and second elevation curves can be achieved by these curves relative to one another are arranged offset in angle. This angular offset can also be realized without varying the stroke, so that the valve drive acts as a phase converter. 6, a line 26 shows the congruent main axes of the in-phase elevation curves 17 and 18, while a dashed line 27 shows the main axis of an out-of-phase elevation curve.

Claims (10)

  1. A valve drive for an internal combustion engine, having a bearing-mounted camshaft and at least one axially displaceable cam operating at least one gas exchange valve with interposition of a transmission member, characterised in that the cam is formed as a rotationally fixed sliding cam displaceable relative to the camshaft (2) and, axially prestressed in a first position (S1), rests positively against a stop (7) formed between the sliding cam (3) and the transmission member (5).
  2. A drive according to claim 1, characterised in that a portion (21) of one of the faces (8) of the sliding cam (3) rests against the stop (7), the said portion (21) being defined by the lobe curve (18) of the said sliding cam (3).
  3. A drive according to claim 2, characterised in that the stop (7) is formed by a stepped recess (20) provided on the transmission member (5).
  4. A drive according to claim 3, characterised in that two stops (7), acting in opposition and located opposite each other in the longitudinal direction (L) of the camshaft (2), are formed on the transmission member (5).
  5. A drive according to claim 2, characterised in that the stop (7) is formed by a lateral surface (23) of the transmission member (5), the said lateral surface (23) facing the portion (21).
  6. A drive according to claim 3 or 5, characterised in that the portion (21) separates two lobe curves (17, 18) formed on a sliding cam (3).
  7. A drive according to claim 6, characterised in that the sliding cam (3) acts on the transmission member (5) with one lobe curve (17, 18) in the first position (S1) and with the other lobe curve (18, 17) in the second position (S2).
  8. A drive according to claim 3, characterised in that sliding cams (3), provided with a single lobe curve, are arranged adjacently on either side of a fixed cam (15) on the camshaft (2) and act on the transmission member (5) in the first position (S1).
  9. A drive according to one or more of the preceding claims, characterised in that the sliding cam (3) is displaced from one of the positions (S1, S2) into the other position (S2, S1) under the action of a hydraulically operated piston (10).
  10. A drive according to one or more of the preceding claims, characterised in that a positive-locking, rotationally fixed guide (4), extending in the longitudinal direction (L), is arranged between the camshaft (2) and the sliding cam (3).
EP93115881A 1992-10-30 1993-10-01 Internal combustion engine valve drive Expired - Lifetime EP0595060B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4236655A DE4236655A1 (en) 1992-10-30 1992-10-30 Valve drive for an internal combustion engine
DE4236655 1992-10-30

Publications (2)

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EP0595060A1 EP0595060A1 (en) 1994-05-04
EP0595060B1 true EP0595060B1 (en) 1995-12-13

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US (1) US5359970A (en)
EP (1) EP0595060B1 (en)
JP (1) JPH06212923A (en)
DE (2) DE4236655A1 (en)

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Also Published As

Publication number Publication date
JPH06212923A (en) 1994-08-02
US5359970A (en) 1994-11-01
DE59301164D1 (en) 1996-01-25
EP0595060A1 (en) 1994-05-04
DE4236655A1 (en) 1994-05-05

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