EP0970300A1 - Valve gear for gas exchange valves of internal combustion engines - Google Patents

Valve gear for gas exchange valves of internal combustion engines

Info

Publication number
EP0970300A1
EP0970300A1 EP98916971A EP98916971A EP0970300A1 EP 0970300 A1 EP0970300 A1 EP 0970300A1 EP 98916971 A EP98916971 A EP 98916971A EP 98916971 A EP98916971 A EP 98916971A EP 0970300 A1 EP0970300 A1 EP 0970300A1
Authority
EP
European Patent Office
Prior art keywords
tappet
valve
gas exchange
drive according
valve drive
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.)
Withdrawn
Application number
EP98916971A
Other languages
German (de)
French (fr)
Inventor
Daniel Herbst
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.)
Mercedes Benz Group AG
Original Assignee
DaimlerChrysler AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by DaimlerChrysler AG filed Critical DaimlerChrysler AG
Publication of EP0970300A1 publication Critical patent/EP0970300A1/en
Withdrawn legal-status Critical Current

Links

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
    • F01L1/14—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
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/0005—Deactivating 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
    • 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
    • F01L2013/0089—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 with means for delaying valve closing
    • F01L2013/0094—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 with means for delaying valve closing with switchable clamp for keeping valve open

Definitions

  • Vfinf -i 1 antri eb for ffa ⁇ wech ⁇ el v n le by Brp ⁇ n ra f t-.ms sr i npn
  • the invention relates to a valve drive for gas exchange valves of internal combustion engines with the features according to the preamble of claim 1.
  • the generic valve drives are used on the one hand to switch off individual or several valves or on the other hand to switch from one stroke characteristic to another in the same valve.
  • Valves of individual cylinders are switched off in gasoline engines in order to avoid the gas exchange losses on the switched-off cylinders — and to work with a higher medium pressure in the remaining fired cylinders, which increases the thermal efficiency. Consumption and exhaust gas in the partial load range are reduced accordingly.
  • the charge change causes significantly lower losses.
  • the intake swirl in the combustion chamber can be influenced as a function of the speed and thus the combustion can be improved.
  • valve's stroke characteristics can be changed in several ways by the valve switchover, both with regard to the opening stroke and with regard to the control times. With two different stroke characteristics, the control times for two speed ranges can be optimized. be lubricated, which results in consumption and exhaust gas advantages.
  • valve actuators for gas exchange valves which have a device for switching off or switching over a gas exchange valve, e.g. DE 42 13 147 AI, DE 43 33 927 AI, DE 44 05 189 C2 and DE 44 43 101 AI. There are basically two different systems.
  • a first, DE 44 43 101 AI, has a pressure medium chamber within a tappet, which is filled or emptied with oil in order to switch the gas exchange valve on or off.
  • a high oil pressure is required to transmit the actuation forces, which makes simple sealing difficult and requires a complex pressure medium supply. Both the seal than the Pressure also k food supplies take up much space.
  • the gas exchange valves are switched by form-fit, switchable coupling elements, e.g. Pins, bolts or washers, switched on or off, which are arranged between a tappet and the gas exchange valve.
  • the arrangement and actuation of the form-fit coupling elements also take up considerable space.
  • an impermissibly high surface pressure and associated wear can occur in the coupling point if a complete positive fit is not achieved when engaging. Annoying coupling noise can also occur.
  • the object of the invention is to reduce the construction costs of generic valve actuators and to improve their efficiency with a small construction volume. It is solved according to the invention by the features of claim 1.
  • a switchable clamping device is provided as the coupling element, no hydraulic pressure needs to be built up to transmit the actuating forces from the cam to the gas exchange valve.
  • the forces for switching the clamping device device are small and can be applied electrically or by a low oil pressure that is easy to seal and can be generated by a lubricating oil pump.
  • the clamping device works silently and continuously. It is able to automatically compensate for manufacturing tolerances, wear and play due to different operating temperatures. If gas exchange valves are only to be switched on and off, an additional device to compensate for valve clearance can be dispensed with.
  • a simple, space-saving clamping device is achieved with a clamping ring which, with its conical surface, interacts with a corresponding counter surface on the tappet.
  • the conical surfaces can also be on the side towards the inner plunger or on both sides, but it is usually sufficient if the clamping ring has a conical surface on only one side.
  • the cone angle is dimensioned so small that self-locking occurs in an S position of the clamping ring that transmits the actuating force.
  • large actuation forces can be transmitted to the gas exchange valve in a force-locking manner without the need to apply energy for additional holding forces.
  • the clamping ring is only held by one or more compression springs in a position in which the conical surfaces touch slightly, so that the frictional forces required for self-locking take effect.
  • the clamping ring is expediently divided in the axial direction in a sector-like manner.
  • Oil pressure is applied to the clamp ring to release the clamp connection.
  • the lubricating oil pressure of the internal combustion engine is expediently used. This is sufficient since only a small pressure is required to loosen as long as the cam does not actuate the tappet. Does it work Cam on the tappet after the clamp connection is released, this is moved against the force of a first compression spring in the direction of the gas exchange valve without the gas exchange valve opens.
  • the clamping body having a second conical surface which forms an obtuse angle with the first and is brought into effect by the oil pressure against the force of the second compression spring.
  • the cone angle is chosen so large that no self-locking occurs.
  • the second clamp connection keeps the tappet in a bottom dead center position as long as the oil pressure is active. Friction losses between the bucket tappet and the cam and the cylinder head are thus avoided.
  • the second compression spring can overcome the clamping effect, which is supported by the first compression spring, and release the clamping connection.
  • the first compression spring presses the bucket tappet against the base circle of the camshaft. This compensates for any valve play that may be present.
  • An additional device for compensating the valve clearance is not necessary.
  • a limited residual pressure is expediently maintained via a throttle valve and a pressure-maintaining valve in order to improve the response behavior of the switch-off or switching device.
  • the spring chambers are connected to an unpressurized space in the cylinder head.
  • FIG. 1 is a partial cross section through a valve drive with a schematic representation of a pressure supply
  • FIG. 3 shows a detail III in FIG. 1,
  • Fig. 4 shows a detail corresponding to Fig. 3, but in a different switching position
  • Fig. 5 shows a valve drive with a valve switch.
  • a camshaft 1 rotates in the direction of the arrow and describes a dashed circle with its cam 2.
  • the distance between the dashed circle and the base circle of the camshaft 1 corresponds to the stroke of the cam 2, which actuates a tappet 6 guided in a cylinder head 5 and shifts it to a bottom dead center position.
  • a first compression spring 14 presses the bucket tappet 6 against the camshaft 1 or the cam 2. It is supported on an inner tappet 7 which is guided in the bucket tappet 6 and bears against a valve stem 8 of a gas exchange valve.
  • This has a valve plate 9 with a valve seat 11, which is held by a valve spring 12 sealingly against a valve seat ring 10 and thus closes a gas exchange duct 13 to a combustion chamber, not shown, of an internal combustion engine.
  • the clamping ring 15 has a first conical surface 17 which, due to the force F C2 of a second compression spring 16, bears against a first conical counter surface 18 in the tappet 6.
  • the second compression spring 16 can consist of several individual springs.
  • the first conical surface 17 or the first conical counter surface 18 has a cone angle ⁇ ⁇ ; which is dimensioned so that self-locking occurs through friction. It must therefore be ⁇ 2 smaller than the arc tangent of the minimal, to be expected friction coefficient ⁇ min between the tappet 6 and the clamping ring 15.
  • a force is generated by the force F N of the cam 2 and the force F v of the valve spring 12 via the normal forces N x and N 2 without additional holding forces having to be applied.
  • the forces F C1 of the first compression spring 14 are negligibly small.
  • the frictional forces R x and R 2 act in the direction of the contact surfaces between the cup tappet 6 or the inner tappet 7 on the one hand 'and the clamping ring 15 on the other hand.
  • the clamp connection can be released with a relatively low pressure P, which is applied by a pressure oil pump 25, for example a lubricating oil pump of the internal combustion engine, via a solenoid valve 24 and a pressure channel 23.
  • a pressure oil pump 25 for example a lubricating oil pump of the internal combustion engine
  • the clamping ring 15 has a second conical surface 19 which interacts with a second conical counter surface 20.
  • the cone angle ⁇ 2 is designed so that it under which oil pressure produces a sufficient clamping connection to hold the tappet 6 against the force F C1 of the first compression spring 14 in the bottom dead center position. There is no self-locking, so that the clamp connection is automatically released under the influence of the second compression spring 16 as soon as the oil pressure P has dropped accordingly.
  • a pressure control valve 26 in conjunction with a throttle 31 ensures that there is always a certain upstream pressure in the pressure chamber 22 and in the pressure channel 23, as a result of which the response behavior of the clamping device is improved.
  • the clamping ring 15 is divided into four sectors in the axial direction. A simple assembly and a good contact of the conical surfaces 17 and 19 on the corresponding counter surfaces 18 and 20 is thereby achieved.
  • the oil control f lu ß by gaps 21, which are formed by the sectors of the clamping ring 15 is kept small, it is expedient to seal the gaps 21 on the pressure side or on the side of the second compression spring 16 with a cylindrical sealing ring 30 or elastic.
  • the seal on the compression spring side has the advantage that the pressure oil reliably releases the first clamping connection by penetrating between the first conical surface 17 and the corresponding first counter surface 18.
  • ventilation openings in the form of a ventilation groove 28 and a ventilation bore 29 are provided.
  • the inner tappet 7 is guided through the bottom of the tappet 6 and is actuated by a central cam 3. Flanking cams 4, which have a different stroke characteristic than the central cam 3, actuate the cup tappet 6.
  • the cup tappet 6 can be coupled to the inner tappet 7 via the clamping ring 15. In the coupled state, the stroke characteristic of the flanking cams 4 acts on the valve. valve stem 8 of the gas exchange valve. If the first clamp connection is released by the oil pressure P and the tappet 6 is held in its bottom dead center position by the second clamp connection, only the stroke characteristic of the middle cam 3 acts on the gas exchange valve. In this way, optimal control times for the gas exchange valve can be achieved for two speed ranges.
  • valve clearance between the flanking cams 4 and the valve stem 8 is compensated for by the clamping ring 15.
  • a special device 27 for compensating for a valve clearance is expediently provided.

Landscapes

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

Abstract

The invention relates to a valve gear for gas exchange valves of internal combustion engines, comprising a cam shaft (1). The cam (2) of this cam shaft (1) acts upon a valve shank (8) of a gas exchange valve via a bucket tappet (6) positioned in a cylinder head (5), an inside tappet (7) being supported on said bucket tappet (6) via a first pressure spring (14). The bucket tappet (6) can be coupled to the inside tappet (7) with a switchable coupling member (15). The gas exchange valve is not operated in the coupled state, provided that it is only driven via the bucket tappet (6). According to the invention, a clamping ring (15) is provided as a switchable coupling member, said clamping ring having a self-locking conical surface (17). The clamping connection can be detached with light oil pressure (P) when the gas exchange valve is closed. This results in a device for switching gas exchange valves off or over which has low frictional loss, is easy to produce, requires little construction space, and can be sealed well because of the low degree of oil pressure (P) required for operation.

Description

Vfinf -i 1 antri eb für ffa πwech πel v n le von Brpπn ra f t-.ms sr i npn Vfinf -i 1 antri eb for ffa πwech πel v n le by Brpπn ra f t-.ms sr i npn
Rps πh rp -i hiingRps πh rp -i hiing
Die Erfindung betrifft einen Ventilantrieb für Gaswechselventile von Brennkraftmaschinen mit den Merkmalen nach dem Oberbegriff von Anspruch 1.The invention relates to a valve drive for gas exchange valves of internal combustion engines with the features according to the preamble of claim 1.
Die gattungsgemäßen Ventilantriebe werden zum einen verwendet, um einzelne oder mehrere Ventile abzuschalten oder zum anderen, um bei dem gleichen Ventil von einer Hubcharakteristik zu einer anderen umzuschalten. Bei Ottomotoren werden Ventile einzelner Zylinder abgeschaltet, um an den abgeschalteten Zylindern die Ladungswechselverluste zu—vermeiden und bei den restlichen befeuerten Zylindern mit einem höheren Mitteldruck zu arbeiten, wodurch sich der thermische Wirkungsgrad erhöht. Entsprechend verringert sich der Verbrauch und das Abgas im Teillastbereich.The generic valve drives are used on the one hand to switch off individual or several valves or on the other hand to switch from one stroke characteristic to another in the same valve. Valves of individual cylinders are switched off in gasoline engines in order to avoid the gas exchange losses on the switched-off cylinders — and to work with a higher medium pressure in the remaining fired cylinders, which increases the thermal efficiency. Consumption and exhaust gas in the partial load range are reduced accordingly.
Bei direkt einspritzenden Dieselmotoren verursacht der Ladungs- wechsel deutlich geringere Verluste. Ist jedoch von mehreren Einlaßventilen pro Zylinder ein Teil abschaltbar, kann der Ansaugdrall im Brennraum drehzahlabhängig beeinflußt und damit die Verbrennung verbessert werden.In the case of direct-injection diesel engines, the charge change causes significantly lower losses. However, if a part of several intake valves per cylinder can be switched off, the intake swirl in the combustion chamber can be influenced as a function of the speed and thus the combustion can be improved.
Die Hubcharakteristik eines Ventils kann durch die Ventilum- schaltung in mehrfacher Hinsicht geändert werden, und zwar sowohl in bezug auf den Öffnungshub als auch in bezug auf die Steuerzeiten. Somit können mit zwei unterschiedlichen Hubcharakteristiken die Steuerzeiten für zwei Drehzahlbereiche opti- miert werden, woraus sich Verbrauchs- und Abgasvorteile ergeben.The valve's stroke characteristics can be changed in several ways by the valve switchover, both with regard to the opening stroke and with regard to the control times. With two different stroke characteristics, the control times for two speed ranges can be optimized. be lubricated, which results in consumption and exhaust gas advantages.
Es sind zahlreiche Ventilantriebe für Gaswechselventile bekannt, die eine Vorrichtung zum Abschalten oder Umschalten eines Gaswechselventils haben, z.B. DE 42 13 147 AI, DE 43 33 927 AI, DE 44 05 189 C2 und DE 44 43 101 AI. Dabei kann man grundsätzlich zwei Systeme unterscheiden.Numerous valve actuators for gas exchange valves are known which have a device for switching off or switching over a gas exchange valve, e.g. DE 42 13 147 AI, DE 43 33 927 AI, DE 44 05 189 C2 and DE 44 43 101 AI. There are basically two different systems.
Ein erstes, DE 44 43 101 AI, weist innerhalb eines Stößels eine Druckmittelkammer auf, die mit Öl gefüllt bzw. entleert wird, um das Gaswechselventil zu- bzw. abzuschalten. Zur Übertragung der Betätigungskräfte wird ein hoher Öldruck benötigt, der eine einfache Abdichtung erschwert und eine aufwendige Druckmittel- Versorgung erfordert. Sowohl die Abdichtung als auch die Druckmittelversorgung beanspruchen viel Bauraum.A first, DE 44 43 101 AI, has a pressure medium chamber within a tappet, which is filled or emptied with oil in order to switch the gas exchange valve on or off. A high oil pressure is required to transmit the actuation forces, which makes simple sealing difficult and requires a complex pressure medium supply. Both the seal than the Pressure also k food supplies take up much space.
Bei einem zweiten System, DE 44 05 189 C2 , werden die Gaswechselventile durch formschlüssige, schaltbare Kuppelglieder, z.B. Stifte, Bolzen oder Scheiben, zu- bzw. abgeschaltet, die zwischen einem Tassenstößel -und dem Gaswechselventil angeordnet ' sind. Die Anordnung und Betätigung der formschlüssigen Kuppel- glieder beanspruchen ebenfalls einen beachtlichen Bauraum. Außerdem können eine unzulässig hohe Flächenpressung und ein damit verbundener Verschleiß in der Koppelstelle entstehen, wenn beim Einrücken kein vollständiger Formschluß erzielt wird. Ferner können lästige Koppelgeräusehe auftreten.In a second system, DE 44 05 189 C2, the gas exchange valves are switched by form-fit, switchable coupling elements, e.g. Pins, bolts or washers, switched on or off, which are arranged between a tappet and the gas exchange valve. The arrangement and actuation of the form-fit coupling elements also take up considerable space. In addition, an impermissibly high surface pressure and associated wear can occur in the coupling point if a complete positive fit is not achieved when engaging. Annoying coupling noise can also occur.
Die Aufgabe der Erfindung besteht darin, bei kleinem Bauvolumen den Bauaufwand gattungsgemaßer Ventilantriebe zu reduzieren und ihren Wirkungsgrad zu verbessern. Sie wird erfindungsgemäß durch die Merkmale von Anspruch 1 gelöst .The object of the invention is to reduce the construction costs of generic valve actuators and to improve their efficiency with a small construction volume. It is solved according to the invention by the features of claim 1.
Dadurch daß als Kuppelglied eine schaltbare Klemmvorrichtung vorgesehen ist, braucht zur Übertragung der Betätigungskräfte vom Nocken auf das Gaswechselventil kein hydraulischer Druck aufgebaut zu werden. Die Kräfte zum Schalten der Klemmvorrich- tung sind klein und können elektrisch oder durch einen geringen Öldruck aufgebracht werden, der einfach abzudichten ist und von einer Schmierölpumpe erzeugt werden kann. Ferner ergibt sich gegenüber formschlüssigen Kuppelgliedern der Vorteil, daß die Klemmvorrichtung geräuschlos und stufenlos arbeitet. Sie ist in der Lage, selbsttätig Fertigungstoleranzen, Verschleiß und Spiele infolge unterschiedlicher Betriebstemperaturen auszugleichen. Wenn Gaswechselventile nur zu- und abgeschaltet werden sollen, kann auf eine zusätzliche Vorrichtung zum Ausgleich eines Ventilspiels verzichtet werden.Because a switchable clamping device is provided as the coupling element, no hydraulic pressure needs to be built up to transmit the actuating forces from the cam to the gas exchange valve. The forces for switching the clamping device device are small and can be applied electrically or by a low oil pressure that is easy to seal and can be generated by a lubricating oil pump. Furthermore, compared to positive coupling elements, there is the advantage that the clamping device works silently and continuously. It is able to automatically compensate for manufacturing tolerances, wear and play due to different operating temperatures. If gas exchange valves are only to be switched on and off, an additional device to compensate for valve clearance can be dispensed with.
Eine einfache, raumsparende Klemmvorrichtung erzielt man mit einem Klemmring, der mit seiner konischen Fläche mit einer entsprechenden Gegenfläche am Tassenstößel zusammenwirkt. Die konischen Flächen können sich auch auf der Seite zum inneren Stößel hin oder auf beiden Seiten befinden, jedoch reicht es in der Regel aus, wenn der Klemmring nur auf einer Seite eine konische Fläche besitzt.A simple, space-saving clamping device is achieved with a clamping ring which, with its conical surface, interacts with a corresponding counter surface on the tappet. The conical surfaces can also be on the side towards the inner plunger or on both sides, but it is usually sufficient if the clamping ring has a conical surface on only one side.
Der Konuswinkel ist so klein bemessen, daß in einer die Betätigungskraft übertragenden S-tellung des Klemmrings Selbsthemmung auftritt. Dadurch können große Betätigungskräfte auf das Gaswechselventil kraftschlüsεig übertragen werden, ohne daß Energie für zusätzliche Haltekräfte aufgebracht werden müßte. Der Klemmring wird nur durch eine oder mehrere Druckfedern in einer Position gehalten, in der sich die konischen Flächen leicht berühren, damit die für eine Selbsthemmung erforderlichen Reibkräfte wirksam werden. Um den Klemmring leichter montieren zu können und damit seine konische Fläche besser an der Gegenfläche anliegt, ist der Klemmring zweckmäßigerweise in axialer Richtung sektorförmig geteilt.The cone angle is dimensioned so small that self-locking occurs in an S position of the clamping ring that transmits the actuating force. As a result, large actuation forces can be transmitted to the gas exchange valve in a force-locking manner without the need to apply energy for additional holding forces. The clamping ring is only held by one or more compression springs in a position in which the conical surfaces touch slightly, so that the frictional forces required for self-locking take effect. In order to be able to mount the clamping ring more easily and thus its conical surface lies better against the counter surface, the clamping ring is expediently divided in the axial direction in a sector-like manner.
Der Klemmring wird mit einem Öldruck beaufschlagt, um die Klemmverbindung zu lösen. Hierzu verwendet man zweckmäßigerweise den Schmieröldruck der Brennkraftmaschine. Dieser reicht aus, da zum Lösen nur ein geringer Druck erforderlich ist, solange der Nocken den Tassenstößel nicht betätigt. Wirkt der Nocken auf den Tassenstößel, nachdem die Klemmverbindung gelöst ist, wird dieser entgegen der Kraft einer ersten Druckfeder in Richtung auf das Gaswechselventil verschoben, ohne daß das Gaswechselventil öffnet.Oil pressure is applied to the clamp ring to release the clamp connection. For this purpose, the lubricating oil pressure of the internal combustion engine is expediently used. This is sufficient since only a small pressure is required to loosen as long as the cam does not actuate the tappet. Does it work Cam on the tappet after the clamp connection is released, this is moved against the force of a first compression spring in the direction of the gas exchange valve without the gas exchange valve opens.
Da sich der Tassenstößel im Zylinderkopf bewegt, auch ohne das Gaswechselventil zu betätigen, und am Nocken der Nockenwelle gleitet, entstehen Reibungsverluste. Diese können gemäß einer Ausgestaltung der Erfindung vermieden werden, indem der Klemmkörper eine zweite konische Fläche besitzt, die mit der ersten einen stumpfen Winkel bildet und durch den Öldruck entgegen der Kraft der zweiten Druckfeder zur Wirkung gebracht wird. Der Konuswinkel ist hier so groß gewählt, daß keine Selbsthemmung auftritt. Die zweite Klemmverbindung hält den Tassenstößel in einer unteren Totpunktlage, solange der Öldruck wirkt. Somit werden Reibungsverluste zwischen dem Tassenstößel und dem Nokken sowie dem Zylinderkopf vermieden.Since the bucket tappet moves in the cylinder head, even without actuating the gas exchange valve, and slides on the camshaft cam, friction losses occur. According to one embodiment of the invention, these can be avoided by the clamping body having a second conical surface which forms an obtuse angle with the first and is brought into effect by the oil pressure against the force of the second compression spring. The cone angle is chosen so large that no self-locking occurs. The second clamp connection keeps the tappet in a bottom dead center position as long as the oil pressure is active. Friction losses between the bucket tappet and the cam and the cylinder head are thus avoided.
Wenn der Klemmring druckentlastet ist, kann die zweite Druckfeder die Klemmwirkung, die durch die erste Druckfeder unterstützt wird, überwinden und die Klemmverbindung lösen. Die erste Druckfeder drückt dabei den Tassenstößel gegen den Grundkreis der Nockenwelle . Dadurch wird eventuell vorhandenes Ventilspiel ausgeglichen. Eine zusätzliche Vorrichtung zum Ausgleich des Ventilspiels ist nicht erforderlich. Zweckmäßigerweise wird über ein Drosselventil und ein Druckhalteventil ein begrenzter Restdruck aufrechterhalten, um das Ansprechverhalten der Abschalt- bzw. Umschaltvorrichtung zu verbessern.If the clamping ring is relieved of pressure, the second compression spring can overcome the clamping effect, which is supported by the first compression spring, and release the clamping connection. The first compression spring presses the bucket tappet against the base circle of the camshaft. This compensates for any valve play that may be present. An additional device for compensating the valve clearance is not necessary. A limited residual pressure is expediently maintained via a throttle valve and a pressure-maintaining valve in order to improve the response behavior of the switch-off or switching device.
Damit sich durch Leckage kein Öldruck in den Federräumen der ersten und zweiten Druckfeder aufbauen kann, sind die Federräume mit einem drucklosen Raum im Zylinderkopf verbunden.In order that no oil pressure can build up in the spring chambers of the first and second compression springs due to leakage, the spring chambers are connected to an unpressurized space in the cylinder head.
Weitere Vorteile und Einzelheiten ergeben sich aus der folgenden Zeichnungsbesehreibung . In der Zeichnung sind Ausführungsbeispiele der Erfindung dargestellt. In der Beschreibung und in den Ansprüchen sind zahlreiche Merkmale im Zusammenhang dargestellt und beschrieben. Der Fachmann wird die Merkmale zweckmäßigerweise auch einzeln betrachten und zu sinnvollen Kombinationen zusammenfassen.Further advantages and details result from the following description of the drawing. Exemplary embodiments of the invention are shown in the drawing. Numerous features are shown and described in connection in the description and in the claims. The person skilled in the art will expediently also consider the features individually and combine them into meaningful combinations.
Es zeigen:Show it:
Fig. 1 einen teilweisen Querschnitt durch einen Ventilantrieb mit einer schematischen Darstellung einer Druckversorgung,1 is a partial cross section through a valve drive with a schematic representation of a pressure supply,
Fig. 2 einen Querschnitt entsprechend der Linie II - II in Fig. 1,2 shows a cross section along the line II-II in FIG. 1,
Fig. 3 ein Detail III in Fig. 1,3 shows a detail III in FIG. 1,
Fig. 4 ein Detail entsprechend Fig. 3, jedoch in einer andern Schaltposition undFig. 4 shows a detail corresponding to Fig. 3, but in a different switching position and
Fig. 5 einen Ventilantrieb mit einer Ventilumschaltung.Fig. 5 shows a valve drive with a valve switch.
Eine Nockenwelle 1 dreht sich in Pfeilrichtung und beschreibt dabei mit ihrem Nocken 2 einen gestrichelten Kreis . Der Abstand zwischen dem gestrichelten Kreis und dem Grundkreis der Nockenwelle 1 entspricht dem Hub des Nockens 2, der einen in einem Zylinderkopf 5 geführten Tassenstößel 6 betätigt und diesen bis in eine untere Totpunktlage verschiebt. Eine erste Druckfeder 14 drückt den Tassenstößel 6 in Anlage gegen die Nockenwelle 1 bzw. den Nocken 2. Sie stützt sich an einem inneren Stößel 7 ab, der in dem Tassenstößel 6 geführt ist und an einem Ventil- schaft 8 eines Gaswechselventils anliegt. Dieses besitzt einen Ventilteller 9 mit einem Ventilsitz 11, der von einer Ventilfeder 12 dichtend gegen einen Ventilsitzring 10 gehalten wird und somit einen Gaswechselkanal 13 zu einem nicht näher dargestellten Brennraum einer Brennkraftmaschine hin abschließt.A camshaft 1 rotates in the direction of the arrow and describes a dashed circle with its cam 2. The distance between the dashed circle and the base circle of the camshaft 1 corresponds to the stroke of the cam 2, which actuates a tappet 6 guided in a cylinder head 5 and shifts it to a bottom dead center position. A first compression spring 14 presses the bucket tappet 6 against the camshaft 1 or the cam 2. It is supported on an inner tappet 7 which is guided in the bucket tappet 6 and bears against a valve stem 8 of a gas exchange valve. This has a valve plate 9 with a valve seat 11, which is held by a valve spring 12 sealingly against a valve seat ring 10 and thus closes a gas exchange duct 13 to a combustion chamber, not shown, of an internal combustion engine.
Zwischen dem Tassenstößel 6 und dem inneren Stößel 7 befindet sich ein Kuppelglied in Form eines Klemmrings 15. Dieser bewirkt in Kuppelstellung (Fig. 3) , daß die Betätigungskräfte des Nockens 2 vom Tassenstößel 6 über den inneren Stößel 7 auf den Ventilschaft 8 übertragen werden und das Gaswechselventil entgegen der Kraft der Ventilfeder 12 vom Nocken 2 geöffnet wird.Between the tappet 6 and the inner tappet 7 there is a coupling element in the form of a clamping ring 15. In the coupling position (FIG. 3), this causes the actuating forces of the cam 2 from the tappet 6 via the inner tappet 7 to the Valve stem 8 are transmitted and the gas exchange valve is opened against the force of the valve spring 12 by the cam 2.
Zu diesem Zweck besitzt der Klemmring 15 eine erste konische Fläche 17, die durch die Kraft FC2 einer zweiten Druckfeder 16 an einer ersten konischen Gegenfläche 18 im Tassenstößel 6 anliegt. Die zweite Druckfeder 16 kann aus mehreren einzelnen Federn bestehen.For this purpose, the clamping ring 15 has a first conical surface 17 which, due to the force F C2 of a second compression spring 16, bears against a first conical counter surface 18 in the tappet 6. The second compression spring 16 can consist of several individual springs.
Wie Fig. 3 deutlicher zeigt, hat die erste konische Fläche 17 bzw. die erste konische Gegenfläche 18 einen Konuswinkel αι; der so bemessen ist, daß Selbsthemmung durch Reibung auftritt. Es muß also α2 kleiner als der Arkustangens des minimalen, zu erwartenden Reibungskoeffizienten μmιn zwischen dem Tassenstößel 6 und dem Klemmring 15 sein. In diesem Fall wird durch die Kraft FN des Nockens 2 und die Kraft Fv der Ventilfeder 12 über die Normalkräfte Nx und N2 eine Klemmverbindung erzeugt, ohne daß zusätzliche Haltekräfte aufgebracht werden müßten. Gegenüber diesen Kräften sind die Kräfte FC1 der ersten Druckfeder 14 vernachlässigbar klein. In Richtung der Kontaktflächen zwischen dem Tassenstößel 6 bzw. dem inneren Stößel 7 einerseits' und dem Klemmring 15 andererseits, wirken die Reibungskräfte Rx und R2.As FIG. 3 shows more clearly, the first conical surface 17 or the first conical counter surface 18 has a cone angle α ι; which is dimensioned so that self-locking occurs through friction. It must therefore be α 2 smaller than the arc tangent of the minimal, to be expected friction coefficient μ min between the tappet 6 and the clamping ring 15. In this case, a force is generated by the force F N of the cam 2 and the force F v of the valve spring 12 via the normal forces N x and N 2 without additional holding forces having to be applied. Compared to these forces, the forces F C1 of the first compression spring 14 are negligibly small. The frictional forces R x and R 2 act in the direction of the contact surfaces between the cup tappet 6 or the inner tappet 7 on the one hand 'and the clamping ring 15 on the other hand.
Läuft der Tassenstößel 6 am Grundkreis der Nockenwelle 1, wirken auf den Klemmring 15 nur die Kräfte FC1 und FC2. In dieser Situation kann die Klemmverbindung mit einem relativ geringen Druck P gelöst werden, der von einer Druckölpumpe 25, z.B. einer Schmierölpumpe der Brennkraftmaschine, über ein Magnetventil 24 und einen Druckkanal 23 aufgebracht wird. Im gelösten Zustand kann sich der Tassenstößel 6 gegenüber dem inneren Stößel 7 axial verschieben, ohne daß Betätigungskräfte auf das Gaswechselventil übertragen werden.If the tappet 6 runs on the base circle of the camshaft 1, only the forces F C1 and F C2 act on the clamping ring 15. In this situation, the clamp connection can be released with a relatively low pressure P, which is applied by a pressure oil pump 25, for example a lubricating oil pump of the internal combustion engine, via a solenoid valve 24 and a pressure channel 23. In the released state, the tappet 6 can move axially relative to the inner tappet 7 without actuating forces being transmitted to the gas exchange valve.
Um die Reibungsverluste zu vermindern, wenn keine Betätigungskräfte übertragen werden, besitzt der Klemmring 15 eine zweite konische Fläche 19, die mit einer zweiten konischen Gegenfläche 20 zusammenwirkt. Der Konuswinkel α2 ist so ausgelegt, daß er unter dern Öldruck eine ausreichende Klemmverbindung erzeugt, um den Tassenstößel 6 entgegen der Kraft FC1 der ersten Druckfeder 14 in der unteren Totpunktlage zu halten. Es tritt dabei keine Selbsthemmung auf, so daß sich die Klemmverbindung unter dem Einfluß der zweiten Druckfeder 16 selbsttätig löst, sobald der Öldruck P entsprechend abgefallen ist. Ein Druckhalteventil 26 sorgt in Verbindung mit einer Drossel 31 dafür, daß im Druckraum 22 und im Druckkanal 23 stets ein gewisser Vordruck herrscht, wodurch das Ansprechverhalten der Klemmvorrichtung verbessert wird.In order to reduce the friction losses when no actuation forces are transmitted, the clamping ring 15 has a second conical surface 19 which interacts with a second conical counter surface 20. The cone angle α 2 is designed so that it under which oil pressure produces a sufficient clamping connection to hold the tappet 6 against the force F C1 of the first compression spring 14 in the bottom dead center position. There is no self-locking, so that the clamp connection is automatically released under the influence of the second compression spring 16 as soon as the oil pressure P has dropped accordingly. A pressure control valve 26 in conjunction with a throttle 31 ensures that there is always a certain upstream pressure in the pressure chamber 22 and in the pressure channel 23, as a result of which the response behavior of the clamping device is improved.
Wie Fig. 2 zeigt, ist der Klemmring 15 in axialer Richtung in vier Sektoren geteilt . Dadurch wird eine einfache Montage und eine gute Anlage der konischen Flächen 17 und 19 an den entsprechenden Gegenflächen 18 und 20 erreicht. Damit der Ölabfluß durch Spalte 21, die von den Sektoren des Klemmrings 15 gebildet werden, klein gehalten wird, ist es zweckmäßig, die Spalte 21 druckseitig oder auf der Seite der zweiten Druckfeder 16 mit einem zylindrischen Dichtring 30 oder elastisch abzudichten. Die Dichtung auf der Druckfederseite hat den Vorteil, daß das Drucköl die erste Klemmverbindung sicher löst, indem es zwischen die erste konische Fläche 17 und die entsprechende erste Gegenfläche 18 dringt.2 shows, the clamping ring 15 is divided into four sectors in the axial direction. A simple assembly and a good contact of the conical surfaces 17 and 19 on the corresponding counter surfaces 18 and 20 is thereby achieved. In order that the oil control f lu ß by gaps 21, which are formed by the sectors of the clamping ring 15 is kept small, it is expedient to seal the gaps 21 on the pressure side or on the side of the second compression spring 16 with a cylindrical sealing ring 30 or elastic. The seal on the compression spring side has the advantage that the pressure oil reliably releases the first clamping connection by penetrating between the first conical surface 17 and the corresponding first counter surface 18.
Damit sich durch Leckage kein Öldruck in den Räumen der ersten Druckfeder 14 und der zweiten Druckfeder 16 aufbaut, sind Belüftungsöffnungen in Form einer Belüftungsnut 28 und einer Belüftungsbohrung 29 vorgesehen.So that no oil pressure builds up in the spaces of the first compression spring 14 and the second compression spring 16 due to leakage, ventilation openings in the form of a ventilation groove 28 and a ventilation bore 29 are provided.
Der Ventilantrieb nach Fig. 5 besitzt eine UmsehaltVorrichtung. Hierbei ist der innere Stößel 7 durch den Boden des Tassenstö- ßels 6 geführt und wird von einem mittleren Nocken 3 betätigt. Flankierende Nocken 4, die im Vergleich zum mittleren Nocken 3 eine andere Hubcharakteristik aufweisen, betätigen den Tassenstößel 6. Über den Klemmring 15 kann der Tassenstößel 6 mit dem inneren Stößel 7 gekoppelt werden. Im gekoppelten Zustand wirkt die Hubcharakteristik der flankierenden Nocken 4 auf den Ven- tilschaft 8 des Gaswechselventils. Wird die erste Klemmverbindung durch den Öldruck P gelöst und der Tassenstößel 6 durch die zweite Klemmverbindung in seiner unteren Totpunktlage gehalten, wirkt nur die Hubcharakteristik des mittleren Nockens 3 auf das Gaswechselventil. Somit können für zwei Drehzahlbereiche optimale Steuerzeiten für das Gaswechselventil erzielt werden.5 has a UmsehaltVvorrichtung. Here, the inner tappet 7 is guided through the bottom of the tappet 6 and is actuated by a central cam 3. Flanking cams 4, which have a different stroke characteristic than the central cam 3, actuate the cup tappet 6. The cup tappet 6 can be coupled to the inner tappet 7 via the clamping ring 15. In the coupled state, the stroke characteristic of the flanking cams 4 acts on the valve. valve stem 8 of the gas exchange valve. If the first clamp connection is released by the oil pressure P and the tappet 6 is held in its bottom dead center position by the second clamp connection, only the stroke characteristic of the middle cam 3 acts on the gas exchange valve. In this way, optimal control times for the gas exchange valve can be achieved for two speed ranges.
Das Ventilspiel zwischen den flankierenden Nocken 4 und dem Ventilschaft 8 wird durch den Klemmring 15 ausgeglichen. Um auch das Ventilspiel zwischen dem Ventilschaft 8 und dem mittleren Nocken 3 auszugleichen, wird zweckmäßigerweise eine besondere Vorrichtung 27 zum Ausgleich eines Ventilspiels vorgesehen. The valve clearance between the flanking cams 4 and the valve stem 8 is compensated for by the clamping ring 15. In order to also compensate for the valve clearance between the valve stem 8 and the central cam 3, a special device 27 for compensating for a valve clearance is expediently provided.

Claims

1. Ventilantrieb für Gaswechselventile von Brennkraftmaschinen mit einer Nockenwelle (1) , deren Nocken (2) über einen in einem Zylinderkopf (5) geführten Tassenstößel (6) , an dem sich ein innerer Stößel (7) über eine erste Druckfeder (14) abstützt, auf einen Ventilschaft (8) eines Gaswechselventils wirkt, und mit einem schaltbaren Kuppelglied (15) , das zwischen dem Tassenstößel (6) und dem Umfang des inneren Stößels (7) , der an dem Ventilschaft (8) anliegt, angeordnet ist und eine Kraftübertragung von dem Tassenstößel (6) auf den Ventilschaft (8) ermöglicht, dadurch gekennzeichnet, daß zwischen dem Umfang des inneren Stößels (7) und dem Tassenstößel (6) als Kuppelglied (15) eine schaltbare Klemmvorrichtung angeordnet ist.1. Valve drive for gas exchange valves of internal combustion engines with a camshaft (1), the cams (2) of which are guided by a bucket tappet (6) in a cylinder head (5), on which an inner tappet (7) is supported by a first compression spring (14) , acts on a valve stem (8) of a gas exchange valve, and with a switchable coupling element (15), which is arranged between the bucket tappet (6) and the circumference of the inner tappet (7), which abuts the valve stem (8), and a Power transmission from the tappet (6) to the valve stem (8) enables, characterized in that a switchable clamping device is arranged as a coupling member (15) between the circumference of the inner tappet (7) and the tappet (6).
2. Ventilantrieb nach Anspruch 1, dadurch gekennzeichnet, daß die Klemmvorrichtung (15) einen axial zum Tassenstößel (6) verstellbaren Klemmring (15) mit einer konischen Fläche (17) hat, die mit einer konischen Gegenfläche (18) am Tassenstößel (6) und/oder am inneren Stößel (7) zusammenwirkt und der Konuswinkel so gewählt ist, daß in einer kraftschlüssigen Stellung Selbsthemmung auftritt .2. Valve drive according to claim 1, characterized in that the clamping device (15) has an axially adjustable to the tappet (6) adjustable clamping ring (15) with a conical surface (17) with a conical counter surface (18) on the tappet (6) and / or cooperates on the inner plunger (7) and the cone angle is selected so that self-locking occurs in a non-positive position.
3. Ventilantrieb nach Anspruch 2, dadurch gekennzeichnet, daß der Klemmring (15) in Klemmrichtung von einer zweiten Druckfeder (16) belastet wird und in der entgegengesetzten Richtung von einem Öldruck (P) beaufschlagbar ist.3. Valve drive according to claim 2, characterized in that the clamping ring (15) is loaded in the clamping direction by a second compression spring (16) and can be acted upon in the opposite direction by an oil pressure (P).
4. Ventilantrieb nach Anspruch 3, dadurch gekennzeichnet, daß die die erste (14) bzw. zweite Druckfeder (16) umschließenden Räume über Belüftungsöffnungen (28, 29) mit einem drucklosen Raum im Zylinderkopf (5) verbunden sind. 4. Valve drive according to claim 3, characterized in that the first (14) or second compression spring (16) enclosing spaces via ventilation openings (28, 29) are connected to an unpressurized space in the cylinder head (5).
5. Ventilantrieb nach einem der Ansprüche 2 bis 4, dadurch gekennzeichnet, daß der Klemmring (15) sektorförmig axial geteilt ist .5. Valve drive according to one of claims 2 to 4, characterized in that the clamping ring (15) is axially divided in sectors.
6. Ventilantrieb nach Anspruch 5, dadurch gekennzeichnet, daß Spalte (21) zwischen den Sektoren des Klemmrings (15) durch einen zylindrischen Dichtring (30) abgedichtet sind.6. Valve drive according to claim 5, characterized in that gaps (21) between the sectors of the clamping ring (15) are sealed by a cylindrical sealing ring (30).
7. Ventilantrieb nach Anspruch 6, insoweit dieser auf Anspruch 3 rückbezogen ist, dadurch gekennzeichnet, daß der Dichtring (30) auf der Seite der zweiten Druckfeder (16) angeordnet ist.7. Valve drive according to claim 6, insofar as this is related to claim 3, characterized in that the sealing ring (30) is arranged on the side of the second compression spring (16).
8. Ventilantrieb nach einem der Ansprüche 2 bis 6, dadurch gekennzeichnet, daß der Klemmring (15) eine zweite konische Fläche (19) besitzt, die mit der ersten einen stumpfen Winkel bildet und durch den Öldruck (P) entgegen der Kraft (FC2) der zweiten Druckfeder (16) zur Wirkung gebracht wird, wobei der zweite Konuswinkel α2 so groß gewählt ist, daß keine Selbsthemmung auftritt .8. Valve drive according to one of claims 2 to 6, characterized in that the clamping ring (15) has a second conical surface (19) which forms an obtuse angle with the first and by the oil pressure (P) against the force (F C2 ) the second compression spring (16) is brought into effect, the second cone angle α 2 being chosen so large that no self-locking occurs.
9. Ventilantrieb nach einem der Ansprüche 2 bis 8, dadurch gekennzeichnet, daß der Klemmring (15) mit einem Vordruck beaufschlagt wird.9. Valve drive according to one of claims 2 to 8, characterized in that the clamping ring (15) is acted upon by a pre-pressure.
10. Ventilantrieb nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß der innere Stößel (7) den Tassenstößel (6) zur Nockenwelle (1) hin durchdringt und von einem mittleren Nocken (3) betätigt wird, während zwei flankierende Nokken (4) den Tassenstößel (6) betätigen.10. Valve drive according to one of the preceding claims, characterized in that the inner tappet (7) penetrates the tappet (6) to the camshaft (1) and is actuated by a central cam (3), while two flanking cams (4) Press the cup tappet (6).
11. Ventilantrieb nach Anspruch 10, dadurch gekennzeichnet, daß zwischen dem inneren Stößel (7) und dem Ventilschaft (8) eine Vorrichtung (27) zum Ausgleich eines Ventilspiels vorgesehen ist. 11. Valve drive according to claim 10, characterized in that between the inner plunger (7) and the valve stem (8) a device (27) is provided to compensate for a valve clearance.
EP98916971A 1997-03-26 1998-03-17 Valve gear for gas exchange valves of internal combustion engines Withdrawn EP0970300A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19712668A DE19712668C1 (en) 1997-03-26 1997-03-26 Actuator for valves of internal combustion engine
DE19712668 1997-03-26
PCT/EP1998/001531 WO1998042961A1 (en) 1997-03-26 1998-03-17 Valve gear for gas exchange valves of internal combustion engines

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EP0970300A1 true EP0970300A1 (en) 2000-01-12

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US (1) US6293239B1 (en)
EP (1) EP0970300A1 (en)
JP (1) JP2000510546A (en)
DE (1) DE19712668C1 (en)
WO (1) WO1998042961A1 (en)

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US6293239B1 (en) 2001-09-25
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JP2000510546A (en) 2000-08-15
WO1998042961A1 (en) 1998-10-01

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