EP2013451B1 - Desmodromic control for a lifting valve of an internal combustion engine - Google Patents

Description

Field of the invention

The invention relates to a positive control for at least one lift valve of an internal combustion engine, with a camshaft having at least one Öffnernocken and at least one closer cam, which Öffnernocken the lift valve via a mounted in a longitudinal guide of the engine and a Abgriffsfläche for Öffnernocken having Öffnerstößel operated in the opening direction and which closing cam the lift valve is actuated in the closing direction via a rocker arm mounted in the internal combustion engine.

Background of the invention

Such a forced control, which is also referred to as desmodromic valve control, goes out of the generic DE 35 39 812 A1 out. The rocker arm which actuates the lifting valve in the closing direction is, guided by the camshaft, guided in an arc around the longitudinal guide of the opener tappet and accordingly designed to be wide. The associated lack of rigidity of the rocker arm can then be compensated only by the illustrated material and thus mass and inertia-intensive design or possibly by the use of material-saving, but relatively expensive high-strength materials to produce sufficient structural strength of the rocker arm. In any case, however, the sweeping design of the rocker arm contributes significantly to a limitation of the valve train stiffness, so that the achievement of an essential objective of such positive controls, namely the high speed resistance of the valve train, at least in question.

This problem concerns in the same way also in the DE 41 09 666 A1 proposed positive control with a similarly designed rocker arm. Furthermore, in the JP 61011408 A proposed a positive control in which a longitudinally movably guided hydraulic valve clearance compensation device is arranged between the cam-side Kipphebelarm and the closing cam. In this valve control, however, instead of the longitudinally guided Öffnerstößels a supported on a stationary pivot bearing rocker arm for actuating the lift valve in the opening direction is provided. Irrespective of this, the rocker arm which is designed to be wide in this document is also disadvantageous in terms of the valve train rigidity and, in particular, in connection with the oppositely disposed rocker arm, also with regard to the claimed installation space.

Object of the invention

The invention is therefore based on the object to avoid these disadvantages and thus to provide a positive control whose stiffness also allows operation of the internal combustion engine at very high speeds and which is also characterized by a compact and space-saving design.

Summary of the invention

This object is achieved in that an adjacent to the longitudinal guide extending further longitudinal guide is provided in which further longitudinal guide is arranged between the closing cam and the rocker arm closer tappet is mounted with a tap surface for the closing cam. The adjacent arrangement of the longitudinal guides with the Öffnerstößel and the closer plunger allows a compact design of the positive control and in particular also of the rocker arm in favor of the greatest possible valve train stiffness with a comparatively small space requirement.

This is according to a preferred embodiment of the invention, especially when the longitudinal guide and the further longitudinal guide axially parallel to each other and preferably axially parallel to the lift valve.

Furthermore, a first arm of the rocker arm with a cam-distant plunger bottom of the Öffnerstößels and a second arm of the rocker arm cooperate with a cam-distant plunger bottom of the closer plunger, wherein the Öffnerstößel for transmitting acting in the closing direction tensile forces on the lift valve force, form or cohesively with the shaft end connected is. Compared to the solutions proposed in the cited prior art, in which the rocker engages under a connected to the lifting valve spring-like component for transmitting acting in the closing direction tensile forces in the longitudinal axis of the lift valve, exist by this inventive design extensive freedom in terms of kinematic interaction of the rocker arm with the opener and closer tappets. Thus, the decoupled from the rocker arm tension-pressure connection of the Öffnerstößels with the lifting valve allows an articulation of the Kipphebelarme as far as possible spaced contact points of the Öffner- and the closer plunger corresponding to large lever arms to keep the leverage despite the compact design of the positive control as low as possible.

Taking into account the kinematically caused transverse displacement of the rocker arm arms relative to the plunger bottoms, it can be provided that a push rod mounted on both sides is arranged between one or both arms and the associated plunger bottoms.

In addition, the rocker arm may be formed cross-shaped and supported with a third arm and with a fourth arm on stationary mounted in the engine pivot bearings, of which preferably a pivot bearing is provided with a hydraulic clearance compensation. Such pivot bearings, for example, as known in the art, used for the storage of rocker arms supporting elements with or without hydraulic Play compensation be formed. The hydraulic clearance compensation serves in the present case to compensate for the component tolerances and wear as well as by different thermal expansions game between the closed globe valve and the closing cam.

In an advantageous embodiment of the invention, the Öffnerstößel a pot-like outer part with a serving for storage in the longitudinal guide plunger shirt and the plunger bottom and an outer part received in the inner part, on which the Abgriffsfläche for the Öffnernocken and arranged on a cam-distal bottom portion of the inner part valve stem support are arranged include. In this case, pressure forces acting in the opening direction on the front side over the Ventilschaftauflage and acting in the closing direction tensile forces circumferentially in the projecting through a recess of the plunger bottom into the outer part shaft end of the lift valve via a transmission device which extends between the plunger bottom and the shaft end initiated. Such a trained Öffnerstößel forms the basis for a mounting-friendly and space-saving train-duck connection of the Öffnerstößels with the globe valve. Moreover, in the event that such an opener tappet and the closer plunger are formed as equal parts, the potential of low manufacturing costs of the positive control can be opened up.

Furthermore, there is a structurally particularly simple solution for the transmission device is that this is supported on the plunger bottom ring with an opening in the direction of the camshaft inner cone and clamping wedges, which engage in one or more molded on the shaft end recesses and on its outer circumferential surface complementary to the inner cone Form outer cone includes. In addition to the ability to transmit the well-known from conventional valve controls and mature connection of the spring plate to the lift valve by means of clamping wedges on the present positive control, also conventional globe valves and slips can be used without further modifications.

Furthermore, a structurally simple, space-saving and cost-effective valve clearance compensation between the closed lift valve and the Öffnernocken take place characterized in that the valve stem support is formed on a between the shaft end and the cam-distal bottom portion of the inner part Ventilspieleinstellscheibe with a given thickness. Although opener side basically a hydraulic valve clearance compensation can be provided, the mechanical clearance compensation in the form of Ventilspieleinstellscheibe prevents unfavorable mutual influence of hydraulic valve clearance compensation elements, which are provided both opener side and closing side. This influence can lead to malfunctions of the internal combustion engine as a result of a no longer completely closing globe valve on the one hand or even destruction of the engine as a result of a tearing valve due to high valve seat forces on the other hand.

In a further development of the invention, an insert mounted in the internal combustion engine is provided, in which the longitudinal guide and the further longitudinal guide extend, and an axis supporting the rocker arm is fastened. By such an insert ideal conditions for a montage-friendly and cost-effective modular design of the forced control are created, since the components essential for the Hubübertragung between the camshaft and the globe valve are arranged in the insert part. This relates in particular to the axle-mounted rocker arm, which can be fastened to the insert part with comparatively little effort outside the internal combustion engine.

It is also contemplated that the insert member is longitudinally movably mounted in a hollow cylindrical recess of the internal combustion engine, wherein between a base of the recess and a bottom of the insert facing the ground, a hydraulic clearance compensation element is arranged, which forces the insert part in the direction of the camshaft. For this purpose, preferably the use of valve clearance compensation elements, as they are known as a housing, a pressure piston, a compression spring and a check valve comprehensive assembly unit of conventional bucket tappet or rocker arm valve drives.

The valve seat force of the closed lift valve with respect to the valve seat generated in conventional valve controls is usually generated in forced controls by a defined and starting from the closing cam tension of the valvetrain members by the closing cam pulls the lift valve via the closer plunger and the rocker arm in the valve seat. However, in the case of the clearance compensation element clamped between the insert part and the internal combustion engine, which has to absorb the support forces generated, it should be noted that the clearance compensation element is in the state of load freedom required for the compensation process for a sufficiently long period of time. In order to safely exclude an unwanted lifting of the lift valve from the valve seat, and at the same time to meet the requirement of temporary load freedom of the hydraulic lash adjuster, the closer cam in development of the invention should have a Grundkreisphase superimposed additional lift to increase the valve seat force of the lift valve. The beginning of such a supplementary stroke is expediently to be positioned on the base circle such that the angular range between the currently closed lifting valve and the additional stroke corresponds to a time period which is always sufficient for the balancing phase of the clearance compensation element.

In combination or alternatively, the valve seat force can also be increased by the fact that the insert part is additionally subjected to a force in the direction of the camshaft by a spring means connected in parallel to the lash adjuster element and clamped between the bottom of the recess and the bottom of the insert part. The increase in valve seat force can be expedient or necessary, in particular in supercharged internal combustion engines, since increased gas pressures act in the opening direction of the lift valve both in the intake and in the exhaust gas duct.

To reduce the friction of the positive control also the Abgriffsfläche the Öffnerstößels and / or the Abgriffsfläche of the closer plunger are designed to be rotatable and optionally roller bearings rollers.

In a further embodiment of the invention, the camshaft is part of a camshaft system known per se with at least one actuator axially displaceable cam piece, the at least two juxtaposed Öffnernocken and at least two juxtaposed closing cam each with different cam elevations and / or phases at the same base circle diameters having. The inventive combination of the present positive control with the known camshaft system makes it possible to significantly mitigate the rigidly required in rigid cam surveys compromise in terms of partially conflicting engine targets torque, power, fuel consumption and exhaust emissions. This is particularly beneficial for the positive control present here with the considerable potential for increasing the speed of the internal combustion engine, since in this case no speed-limiting influences exist on the part of a valve spring acting on the gas exchange valve in the closing direction. Otherwise it would be even more difficult with just one survey of the gas exchange valve for the entire and then very wide speed range to meet all the above target sizes equally satisfying. For example, the valve timing of a positive control to produce the highest possible power to the occurring at very high speeds gas-dynamic effects during the charge change may be adjusted by the valve timing lead to a long valve duration at high maximum stroke and a large overlap between the exhaust and intake valves. However, such a timing characteristics is contrary to the residual gas-sensitive idling and idle operating points of the internal combustion engine, since the focus here on short valve opening times and small valve overlaps at moderate valve strokes to produce lowest exhaust emissions with the best possible concentricity quality of the engine. In this respect, for example, a first Öffnernocken and the associated closer cam to meet the engine requirements for idling and part load operating points of the engine could be adjusted while a second Öffnernocken and a second associated Schließernocken in terms of a full torque curve with the greatest possible performance Internal combustion engine can be tuned.

In a particularly preferred embodiment of such a variable positive control, the adjusting device may comprise fixedly arranged in the internal combustion engine actuators and at both ends of the cam piece extending cylindrical sections in which each circumferentially a helical Verschiebenut that is mirror-symmetrical to the other displacement groove of the cam piece is formed, wherein the independently controllable actuators are alternately radially retractable into the associated displacement grooves. Accordingly, each shift direction of the cam piece is associated with a separate slide groove and the associated actuator, which dips to initiate the sliding operation in the sliding groove, axially displaces the cam piece and finally returns to its original position, while the cam piece can be locked in its new axial position.

Brief description of the drawings

Figur 1

ein erstes Ausführungsbeispiel einer erfindungsgemäßen Zwangssteuerung mit einer starren Nockenwelle im Längsschnitt;

Figur 2

die Zwangssteuerung gemäß Figur 1 in einer um 90° gedrehten Darstellung;

Figur 3

eine perspektivische Darstellung eines zweiten Ausführungsbeispiels einer erfindungsgemäßen Zwangssteuerung in optionaler Kombination mit einem Nockenschaltsystem;

Figur 4

einen Ausschnitt der Zwangssteuerung gemäß Figur 3 in vergrößerter Darstellung;

Figur 5

ein Einsatzteil gemäß Figur 4 in vergrößert dargestelltem Längsschnitt.

Further features of the invention will become apparent from the following description and from the drawings, in which embodiments of the invention are shown in simplified form. If no other marking is made, functionally identical components are provided with the same reference numbers. Show it:

FIG. 1

a first embodiment of a positive control according to the invention with a rigid camshaft in longitudinal section;

FIG. 2

the compulsory control according to FIG. 1 in a rotated by 90 ° representation;

FIG. 3

a perspective view of a second embodiment of a positive control according to the invention in optional combination with a cam switching system;

FIG. 4

a section of the forced control according to FIG. 3 in an enlarged view;

FIG. 5

an insert according to FIG. 4 in enlarged longitudinal section.

Detailed description of the drawings

The structure and operation of a first embodiment of a positive control 1 a of an internal combustion engine 2 according to the invention is in the Figures 1 and 2 illustrated by a lift valve 3a and a portion of a cooperating with the lift valve 3a camshaft 4a with a rigidly arranged thereon Öffnernocken 5a and a rigidly arranged thereon cam 6a. Shown is a mounted in a longitudinal guide 7a of the internal combustion engine 2 Öffnerstößel 8a formed here as a roller bearing roller 9 Abgriffsfläche 10 for the Öffnernocken 5a and a adjacent to the longitudinal guide 7a further longitudinal guide 11a of the internal combustion engine 2 mounted closer plunger 12a with a also as a roller bearing Roller 13 trained tap area 14 for the closing cam 6a. The Öffnerstößel 8a comprises a cam-side primary plunger 15 and a valve-side secondary plunger 16, which are fixedly connected to one another by a roller 17 which supports the roller 9.

While the primary plunger 15 is substantially identical in construction to the closer plunger 12a, the secondary plunger 16 is non-positively connected to the stem end 18a for transmitting tensile forces acting in the closing direction on the lift valve 3a via a longitudinal compression bandage. The Öffnerstößel 8a and the closer plunger 12a are connected via a mounted in the engine 2 rocker arm 19a and push rods 20, each between a first arm 21 of the rocker arm 19a and a cam-off plunger bottom 22a of the Öffnerstößels 8a and between a second arm 23 of the rocker arm 19a and a cam-distant plunger bottom 24 of the closer plunger 12a are articulated on both sides, in mutual operative connection.

The rocker arm 19a is formed in a cross shape and is supported by a third arm 25 and a fourth arm 26 on pivot bearings 27 and 28 which are mounted stationary in the internal combustion engine 2, wherein the pivot bearing 27 is provided with a hydraulic clearance compensation. Such a pivot bearing 27 is known in the art as such in particular of conventional finger lever valve trains with hydraulic support elements. The fact that the Öffnerstößel 8a is firmly connected via the longitudinal compression bandage in the pulling direction with the lift valve 3a, the pivot bearing 27 can only compensate for mechanical play that occurs with the lift valve 3a closed between the closing cam 6a and a valve seat 29. In contrast, an adjustment of the mechanical clearance between the Öffnernocken 5a and the roller 9 of the Öffnerstößels 8a in this embodiment on the Einpresstiefe of the pressed-in the secondary plunger 16 the lifting valve 3a can be controlled.

In the interaction of the Öffnernockens 5a and the Schließernockens 6a with the characteristic of such positive controls cam profiles, the lift valve 3a is actuated via the Öffnerstößel 8a in the opening direction, while the closer plunger 12a is driven by the pivoting rocker arm 19a and the decreasing stroke of the Schließernockens 6a follows. Analogously, the lifting valve 3a is actuated in the closing direction by the then increasing again stroke of the closing cam 6a the rocker arm 19a pivoted about the closer plunger 12a in the opposite direction, so that the Öffnerstößel 8a followed by the lifting valve 3a then the decreasing stroke of the Öffnernockens 5a , A game created in the component chain between the closer cam 6a and the valve seat 29 by sinking of the loaded during this cycle game pivot bearing 27 game can be compensated in the subsequent phase in which the lift valve 3a is closed by hydraulic adjustment of the pivot bearing 27. This is done on the one hand by contact of the closer plunger 12a to the closer cam 6a and on the other hand by applying force to the opener plunger 8a in the direction of the Öffnernockens 5a to produce a sealing contact force between the lift valve 3a and the valve seat 29th

In FIG. 3 a second embodiment of a positive control 1b according to the invention is disclosed, which with both a rigid camshaft according to the Figures 1 and 2 as well as with a variably shaped camshaft 4b as part of a known per se and explained later camshaft system 30 can be combined. In the positive control 1b, a longitudinally movably mounted in a hollow cylindrical recess 31 of the engine 2 insert part 32 is provided, in which a longitudinal guide 7b for a Öffnerstößel 8b and an adjacent further longitudinal guide 11 b for a Schlie-ßstößel 12b. In the insert 32 also a rocker arm 19b centrally supporting axis 33 is fixed, which extends in a direction orthogonal to the longitudinal axis of the insert member 32 level. The rocker arm 19b is here formed with two arms and is on the both sides hingedly mounted push rods 20 in operative connection with the Öffnerstößel 8b and the closer plunger 12b. As in the first embodiment, the Abgriffsfläche 10 of the Öffnerstößels 8b and the Abgriffsfläche 14 of the Schließerstößels 12b as the Ventiltriebsreib reducing roller bearing rollers 9 and 13 are formed, wherein the Öffnerstößel 8b and the closer plunger 12b respectively via a here designed as a radially protruding needle body anti-rotation 34 relative to the Insert 32 are positioned radially.

The structural design of the Öffnerstößels 8b and the closer plunger 12b is shown in more detail in the sectional view according to FIG. 4 seen. The Öffnerstößel 8b includes a cup-shaped outer part 35, which has a serving for storage in the longitudinal guide 7b plunger shirt 36 and a push rod 20 hingedly mounted plunger bottom 22b, and an outer part 35 recorded inner part 37, in which the axle-mounted roller 9 and one on a cam-distal bottom portion 38 extending valve stem support 39 are arranged. In this case, the valve stem support 39 for adjusting the mechanical clearance between a Öffnernocken 5 b and the end face of a shaft end 18 b of a lift valve 3b on a Ventilspieleinstellscheibe 40 with a given thickness educated.

In order to transmit tensile forces acting in the closing direction on the lifting valve 3b, in this case a form-fitting transmission device 41 is provided between the shaft end 18b and the plunger bottom 22b. The transmission device 41 comprises a ring 42 which is supported on the inside of the plunger 22b and has an inner cone which opens in the direction of the camshaft 4b, and clamping wedges 43 which form an outer cone complementary to the inner cone on its outer circumferential surface and engage in recesses 44 formed on the shaft end 18b.

To reduce the variety of components, the Öffnerstößel 8b and the closer plunger 12b are formed as equal parts and mounted in the insert 32 rotated by 180 ° to each other.

How to include the FIG. 5 becomes clear, for longitudinal support of the insert 32 relative to the internal combustion engine 2, a hydraulic lash adjuster 45 and a spring means 46 connected in parallel therewith provided between a base 47 of the recess 31 and a bottom 47 facing the bottom 48 of the insert 32. The lash adjuster 45 is here as plug-in construction and functional unit, as used in conventional bucket tappet, tilt or rocker arm valve drives, designed and provides analogous to the Figures 1 and 2 relevant embodiments with the lift valve 3b closed for the fact that the insert member 32 is subjected to a force 4b together with the attached rocker arm 19b in the direction of the camshaft shown here simplified. Consequently, a play occurring during the preceding opening phase of the lift valve 3b is compensated for by bringing the follower plunger 12b into abutment with the make cam 6b, while the opener plunger 8b pulls the lift valve 3b into the valve seat 29. The required for a sufficient tightness of the closed lift valve 3b contact forces are increased to the valve seat 29 by the here formed as a helical compression spring spring means 46.

An additional increase in the contact force with respect to the valve seat 29 may be required in particular if the force of the spring means 46 is limited to the space available for the spring means 46 or if the lift valve 3b in the case of a supercharged internal combustion engine by comparatively high pressures Intake or exhaust duct in the opening direction is subjected to force. For this purpose, the closing cam 6b has a supplementary stroke 50 overlapping its base circle phase 49, which additionally applies force to the already closed lifting valve 3b in the direction of the valve seat 29. The here greatly exaggerated shown and limited in practice to a few fractions of a millimeter Zusatzhub 50 is positioned on the Grundkreisphase 49 so that the clearance compensation element 45 for its complete compensation sufficiently long, pressure-force-free period between the currently closed lift valve 3b and the additional stroke 50 is provided.

Below is the above, in FIG. 3 illustrated camshaft system 30 explained. The camshaft 4b comprises a toothed shaft 51 as well as a cam valve 52 which is non-rotatable but axially displaceable for one or more pairs and has an internal toothing complementary to the toothed shaft 51. On the cam piece 52 are each two immediately adjacent arranged Öffnernocken 5 b and 5 c and normally-closed cam 6 b and 6 c. For operating point-dependent adjustment of the height and / or angular position of the valve lift, the Öffnernocken 5 b, 5 c and the closer cam 6 b, 6 c each different cam lobes and / or phases. On the other hand, the pitch circle diameters of the opening cams 5b, 5c and the make cam 6b, 6c are respectively identical to allow unimpeded axial displacement of the cam piece 52 with the lift valves 3b closed. For performing this switching operation, an adjusting device 53 is provided which comprises fixedly arranged in the internal combustion engine 2 actuators 54 and 55 and at both ends of the cam piece 52 extending cylindrical portions 56 and 57. In the sections 56, 57, a helical shift groove 58 and 59 are each circumferentially formed, which is mirror-symmetrical to the other displacement groove 59 and 58, respectively.

Starting from the in FIG. 3 shown switching state of the cam switching system 30 with a large valve lift and long opening duration, a switching to a smaller valve with a smaller opening period is initiated by the fact that the actuator 54 radially retracts into the sliding groove 58 and the rotating cam piece 52 pulls due to the screw to the right. This process is completed when the Öffnocken 5c and the closing cam 6c completely cover the roller 9 of the Öffnerstößels 8b and the roller 13 of the closer plunger 12b and the actuator 54 retracts from the Verschiebenut 58. A renewed switching process back into the illustrated initial state takes place by analogous interaction of the actuator 55 with the displacement groove 59.

LIST OF REFERENCE NUMBERS

1 a, b

Priority

2

Internal combustion engine

3 a, b

globe valve

4 a, b

camshaft

5 a, b, c

Öffnernocken

6 a, b, c

closing cam

7 a, b

longitudinal guide

8 a, b

Öffnerstößel

9

role

10

gripping surface

11 a, b

further longitudinal guidance

12 a, b

NO ram

13

role

14

gripping surface

15

primary plunger

16

secondary plunger

17

bolt

18 a, b

shank end

19 a, b

rocker arm

20

pushrod

21

first arm

22 a, b

tappet bottom

23

second arm

24

tappet bottom

25

third arm

26

fourth arm

27

pivot bearing

28

pivot bearing

29

valve seat

30

Cam Switch System

31

recess

32

insert

33

axis

34

anti-rotation

35

outer part

36

tappet skirt

37

inner part

38

bottom section

39

Valve stem support

40

Ventilspieleinstellscheibe

41

transfer device

42

ring

43

clamping wedge

44

puncture

45

Lash adjuster

46

spring means

47

reason

48

ground

49

Base circle phase

50

Auxiliary

51

splined shaft

52

cam piece

53

locking device

54

actuator

55

actuator

56

cylindrical section

57

cylindrical section

58

shift groove

59

shift groove

Claims (16)

1. Desmodromic control (1a, 1b) for at least one lifting valve (3a, 3b) of an internal combustion engine (2), having a camshaft (4a, 4b) with at least one opener cam (5a, 5b, 5c) and with at least one closer cam (6a, 6b, 6c), which opener cam (5a, 5b, 5c) actuates the lifting valve (3a, 3b) in an opening direction via an opener tappet (8a, 8b) which is mounted in a longitudinal guide (7a, 7b) of the internal combustion engine (2) and which has a pick-off surface (10) for the opener cam. (5a, 5b, 5c), and which closer cam (6a, 6b, 6c) actuates the lifting valve (3a, 3b) in a closing direction via a rocker lever (19a, 19b) mounted in the internal combustion engine (2), characterized in that a further longitudinal guide (11a, 11b) is provided which runs adjacent to the longitudinal guide (7a, 7b), in which further longitudinal guide (11a, 11b) there is mounted a closer tappet (12a, 12b) which is arranged between the closer cam (6a, 6b, 6c) and the rocker lever (19a, 19b) and which has a pick-off surface (14) for the closer cam (6a, 6b, 6c).
2. Desmodromic control (1a, 1b) according to Claim 1, characterized in that the longitudinal guide (7a, 7b) and the further longitudinal guide (11a, 11b) run axially parallel to one another and preferably axially parallel with respect to the lifting valve (3a, 3b).
3. Desmodromic control (1a, 1b) according to Claim 1, characterized in that a first arm (21) of the rocker lever (19a, 19b) interacts with a tappet base (22a, 22b), which is remote from the cam, of the opener tappet (8a, 8b), and a second arm (23) of the rocker lever (19a, 19b) interacts with a tappet base (24), which is remote from the cam, of the closer tappet (12a, 12b), wherein the opener tappet (8a, 8b) is connected in a force-fitting, form-fitting or cohesive manner to the shank end (18a, 18b) of the lifting valve (3a, 3b) for the transmission of tensile forces, acting in a closing direction, to said lifting valve.
4. Desmodromic control (1a, 1b) according to Claim 3, characterized in that in each case one push rod (20), which is articulatedly mounted at both ends, is arranged between one or both arms (21, 23) and the associated tappet bases (22a, 22b, 24).
5. Desmodromic control (1a) according to Claim 3, characterized in that the rocker lever (19a) is of cross-shaped form and is supported by way of a third arm (25) and by way of a fourth arm (26) on pivot bearings (27, 28) mounted in a static manner in the internal combustion engine (2), of which pivot bearings one pivot bearing (27) is preferably provided with hydraulic play compensation.
6. Desmodromic control (1b) according to Claim 3, characterized in that the opener tappet (8b) comprises a pot-like outer part (35) with a tappet skirt (36) which serves for the mounting in the longitudinal guide (7b) and with the tappet base (22b) and comprises an inner part (37) which is received in the outer part (35) and on which are arranged the pick-off surface (10) for the opener cam (5b, 5c) and a valve shank support (39) which runs on a base portion (38), remote from the cam, of the inner part (37), wherein, into that shank end (18b) of the lifting valve (3b) which projects into the outer part (35) through a recess of the tappet base (22b), pressure forces acting in the opening direction are introduced at the face side via the valve shank support (39), and tensile forces acting in the closing direction are introduced at the circumference via a transmission device (41) which runs between the tappet base (22b) and the shank end (18b).
7. Desmodromic control (1b) according to Claim 6, characterized in that the opener tappet (8b) and the closer tappet (12b) are formed as identical parts.
8. Desmodromic control (1b) according to Claim 6, characterized in that the transmission device (41) comprises a ring (42) which is supported on the tappet base (22b) and which has an inner cone, which opens in the direction of the camshaft (4b), and clamping wedges (43) which engage into one or more incisions (44) formed on the shank end (18b) and which, at their outer shell surface, form an outer cone which is complementary to the inner cone.
9. Desmodromic control (1b) according to Claim 6, characterized in that the valve shank support (39) is formed on a valve play setting disc (40) of specified thickness arranged between the shank end (18b) and the base portion (38), which is remote from the cam, of the inner part (37).
10. Desmodromic control (1b) according to Claim 1, characterized in that an insert part (32) is provided which is mounted in the internal combustion engine (2), in which insert part (32) the longitudinal guide (7b) and the further longitudinal guide (11b) extend and an axle (33) which serves for mounting the rocker lever (19b) is fastened.
11. Desmodromic control (1b) according to Claim 10, characterized in that the insert part (32) is mounted in a longitudinally movable manner in a hollow cylindrical recess (31) of the internal combustion engine (2), wherein, between a floor (47) of the recess (31) and a base (48), which faces toward the floor (47), of the insert part (32), there is arranged a hydraulic play compensation element (45), which play compensation element (45) exerts force on the insert part (32) in the direction of the camshaft (4b).
12. Desmodromic control (1b) according to Claim 11, characterized in that the closer cam (6b) has an auxiliary lift (50), which is superposed on its basic circle phase (49), for increasing the valve seat force of the lifting valve (3b).
13. Desmodromic control (1b) according to Claim 11, characterized in that the insert part (32) is additionally acted on with force in the direction of the camshaft (4b) by a spring means (46) which is connected in parallel with the play compensation element (45) and which is braced between the floor (47) of the recess (31) and the base (48) of the insert part (32).
14. Desmodromic control (1a, 1b) according to Claim 1, characterized in that the pick-off surface (10) of the opener tappet (8a, 8b) and/or the pick-off surface (14) of the closer tappet (12a, 12b) are in the form of rotatable rollers (9, 13) which are optionally mounted by means of rolling bearings.
15. Desmodromic control (1b) according to Claim 1, characterized in that the camshaft (4b) is part of a cam switching system (30), which is known per se, with at least one cam piece (52) which can be displaced axially by an actuating device (53) and which has at least two opener cams (5b, 5c) arranged adjacent to one another and at least two closer cams (6b, 6c) arranged adjacent to one another, said cams having cam elevations and/or phases which differ from one another in each case while having the same base circle diameters.
16. Desmodromic control (1b) according to Claim 15, characterized in that the actuating device (53) comprises actuators (54, 55) arranged positionally fixedly in the internal combustion engine (2) and also comprises cylindrical portions (56, 57) which run on both ends of the cam piece (52), into which portions (56, 57) there is formed, on the circumference, in each case one helical displacement groove (58, 59) which is of mirror-symmetrical form with respect to the other displacement groove (59, 58) of the cam piece (52), wherein the actuators (54, 55), which can be actuated independently of one another, can be alternately deployed radially into the associated displacement grooves (58, 59).

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