EP2636859A1 - Valve drive for a combustion engine, and internal combustion engine - Google Patents

Abstract

The valve train (10) has a shift element (24) that is provided for separating and coupling a partial-load rocker arm (14) and a full load rocker arm (13) respectively in inactivated state and activated state. A crank rod (26) is guided either at partial-load rocker arm or at full load rocker arm in thrust direction, such that rocker arms are coupled together in activated state. A cam (17) of cam shaft (16) is defined for displacing the crank rod in relation to the respective cam base circle radially inside a cam contour, in order to ensure the coupling and separation of rocker arms.

Description

The invention relates to a valve train according to the preamble of claim 1 and an internal combustion engine according to the preamble of claim 10.

From the DE 10 2008 027 649 A1 a valvetrain for a marine diesel engine is known. The valve train disclosed therein has a full load rocker arm for operating a valve lifter of a valve of the internal combustion engine in a full load operating range thereof and a part load rocker arm for operating the valve lifter in a part load operating region of the internal combustion engine, the full load rocker arm being rotatable about a lever axis through a first cam of a camshaft, and wherein the part-load rocking lever is rotatable about the lever axis by a second cam of the camshaft. The first cam of the first camshaft for actuating the full load rocker arm has a relation to a cam base circle radially outwardly projecting first cam projection. The second cam of the camshaft, which serves to actuate the part-load rocker arm, has a relation to a cam base circle radially outwardly projecting second cam projection. The valve train disclosed there further has a switching element of a switching pin and a stop. The switching element separates in an inactivated state, the part-load swing lever and the full-load swing lever from each other. In the activated state of the switching element, the same couples the part-load rocker arm and the full-load rocker arm to each other. The stop of the switching element is arranged either on the full load rocker arm or on the part load rocker, wherein the shift pin is slidably guided on the other, ie either on the partial load rocker arm or full load rocker arm in a thrust direction, namely such that the shift pin in the activated state of the switching element via the coupling of part load rocker arm and Volllastschwinghebel a co-rotation of the full load rocker arm with the part load rocker arm causes.

With such a valve train, a valve opening time of gas exchange valves of the internal combustion engine can be changed in order to reduce exhaust emissions of the internal combustion engine.

In the valve train known from the prior art, the switching between the coupling of part load rocker and full load rocker and between the separation of part load rocker and full load rocker is critical, since when switching to the shift pin high forces and moments act, especially when the shift pin in a undefined intermediate position between a fully retracted for the purpose of separating part-load swing lever and full load swing lever and fully extended for coupling full load swing lever and part load swing lever state. In this critical intermediate position there is a risk of plastic component deformations for the shift pin, whereby the shift pin can be damaged and then the valve train of the internal combustion engine fails. This must be avoided.

On this basis, the invention is based on the object to provide a novel valve train and a novel internal combustion engine.

This object is achieved by a valve train according to claim 1. According to the invention, the second cam of the camshaft has a cam contour set back radially inward relative to the respective cam base circle in order to define a defined shifting of the shift pin in the activated state of the shift element in an extension direction of the shift pin as well as for the separation of part load swing lever and full load swing lever for the coupling of part load swing lever and full load swing lever Move the shift pin in the inactivated state of the switching element to ensure in a direction opposite to the retraction direction of retraction of the shift pin.

With the invention, a defined retraction of the shift pin and a defined extension of the shift pin for the separation and coupling of part load swing lever and full load swing lever is guaranteed. Undefined intermediate positions of the shift pin, in which the same is exposed to the risk of plastic component deformation, can be safely and reliably avoided, so that the risk of damage of the shift pin and thus the risk of failure of the valve train over the prior art is reduced.

Preferably, a starting point of the first cam projection and a starting point of the second cam projection on the respective cam base circle at the same circumferential position, as seen in the direction of rotation of the cam, an end point of the second cam projection is behind an end point of the first cam projection on the respective cam base circle, and wherein the radially inward recessed cam contour of the second cam seen in the direction of rotation of the second cam can connect directly to the second cam projection same. The above contouring of the cam projections of the two cams as well as the recessed cam contour of the second cam allow a particularly advantageous actuation, namely coupling and separating, of the oscillating lever.

According to an advantageous embodiment of the invention, the displaceably guided shift pin has a plurality of the same successively positioned grooves in the direction of displacement, which cooperate with a stop forming spring-loaded locking element, such that when the shift pin is fully retracted for separating part-load swing lever and full load swing lever, a seen front end of the same in the extension behind the locking element, and that when the shift pin is fully extended for coupling part-load swing lever and full load swing lever, the front end thereof seen in the extension direction is partially extended against blocking element such that the blocking element in the first groove engages the shift pin, wherein in an intermediate position of the shift pin, the locking element engages in the second groove which is disposed between the first groove and the front end of the shift pin.

Through these details, a defined, multi-stage displacement of the shift pin both during retraction and when extending the same for separating and coupling part-load swing lever and full-load swing lever is further improved.

Preferably, the switching element and thus the switching pin of the same via a hydraulic line with hydraulic pressure can be acted upon, wherein the switching pin has a co-operating with the hydraulic line projection that when extending the same in the activated state of the switching element for coupling part-load rocker and full load rocker first a relatively small hydraulic pressure and then a relatively large hydraulic pressure on the shift pin is effective. As a result, a risk of damage to the cooperating with the switching pin stop is reduced.

According to an advantageous embodiment of the invention are those portions of the shift pin, which act together when displaced with the stop, in the fully retracted position of the shift pin relative to a bearing housing of the shift pin and therefore do not act as a bearing surface.

An internal combustion engine with a valve train is defined in claim 10.

Fig. 1:

eine perspektivische Ansicht eines Ventiltriebs einer Brennkraftmaschine;

Fig. 2:

den Ventiltrieb gemäß Fig. 1 in einer teilweise geschnittenen Ansicht in einer perspektivischen Ansicht von der gegenüberliegenden Seite;

Fig. 3:

den Ventiltrieb gemäß Fig. 1 und 2 in einer Rückansicht;

Fig. 4:

Nockenkonturen des erfindungsgemäßen Ventiltriebs;

Fig. 5:

einen Schaltbolzen und ein federbelastetes Sperrelement des erfindungsgemäßen Ventiltriebs;

Fig. 6:

Details betreffend die Lagerung des Schaltbolzens; und

Fig. 7:

Details betreffend die Beaufschlagung des Schaltbolzens mit Hydraulikdruck.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

Fig. 1:

a perspective view of a valve train of an internal combustion engine;

Fig. 2:

according to the valve train Fig. 1 in a partially sectioned view in a perspective view from the opposite side;

3:

according to the valve train Fig. 1 and 2 in a rear view;

4:

Cam contours of the valve gear according to the invention;

Fig. 5:

a shift pin and a spring-loaded locking element of the valve drive according to the invention;

Fig. 6:

Details concerning the bearing of the shift pin; and

Fig. 7:

Details relating to the application of hydraulic pressure to the shift pin.

The present invention relates to a valve train for an internal combustion engine and an internal combustion engine with such a valve train. Fig. 1 to 3 show different views of a valve train, as in terms of its basic structure of the DE 10 2008 027 649 A1 is known, wherein the disclosure content is hereby incorporated by reference explicitly.

Fig. 1 to 3 show a valve train 10 for driving gas exchange valves of a cylinder of an internal combustion engine, wherein the valve train on the one hand the actuation of a valve lifter 11 for intake valves and on the other hand serves a valve lifter 12 for actuating exhaust valves of the internal combustion engine.

In the concrete case of application, the valve tappet 11 serves to actuate two intake valves of a cylinder of the internal combustion engine and the valve tappet 12 to actuate two exhaust valves of the respective cylinder of the internal combustion engine, such a valvetrain 10 being present for each cylinder of the internal combustion engine. About the intake valves of a cylinder passes compressed charge air into a combustion chamber of the respective cylinder and the exhaust valves passes exhaust gas from the combustion chamber of the respective cylinder, wherein fuel can be introduced via separate injectors into the combustion chamber of the respective cylinder.

The present invention relates to details of the valve train, which serve to actuate the valve stem 11 for the intake valves of a cylinder of an internal combustion engine.

To actuate the valve stem 11 for the intake valves of a cylinder of the internal combustion engine, the valve train 10 in the illustrated embodiment comprises two rocker arms, namely a Volllastschwinghebel 13 for actuating the valve stem 11 in a full load operating range of the internal combustion engine and a part load rocker 14 for actuating the valve stem 11 in a part load operating range of the internal combustion engine , Wherein the Volllastschwinghebel 13 by a first cam 15 of a camshaft 16 and the part-load rocker 14 by a second cam 17 of the camshaft 16 is rotatable about a lever axis 18, for which purpose the Volllastschwinghebel 13 via a first roller 19 on the first cam 15 and Part-load swing lever 14 rolls on a second roller 20 on the second cam 17.

Fig. 3 can be seen that the valve stem 12 is actuated for actuating the exhaust valves of the internal combustion engine by a cam 21 of the camshaft 16, on which rolls a roller 22 of a rocker arm 23 for actuating the valve stem 12.

The valve train of Fig. 1 to 5 has a switching element 24. The switching element 24 is used to switch the valve train 10 between a part-load operation and a full-load operation, wherein the switching element 24 can be acted upon via a hydraulic line 25 with hydraulic pressure to activate the switching element 24. The switching element 24 has a switching pin 26 and a cooperating with the switching pin 26 stop 27th

In the activated state of the switching element 24, that is to say when it is acted upon by hydraulic pressure, the switching pin 26 is displaceable counter to a spring force of a spring element 28 to couple the partial load rocker arm 14 and the full-load rocker arm 13 to each other to ensure the part-load operation.

In the inactivated state of the switching element 24, however, that is, when the same is not applied to hydraulic pressure, the shift pin 26 is displaced by the spring force of the spring member 28 in an opposite direction to separate the partial load rocker and the full load rocker arm to ensure full load operation.

In the inactivated state of the switching element 24 separates the same therefore the part-load rocker 14 and the Volllastschwinghebel 13 from each other and in the activated state thereof, the switching element 24 couples the part-load rocker 14 and the Volllastschwinghebel 13 to each other, wherein the switching pin 26 of the switching element 24 in the activated state of the switching element 24 via the Coupling of partial load rocker arm 14 and full load rocker arm 13 co-rotation of the full load rocker arm 13 with the part-load rocker arm 14 and thus causes or provides a partial load operation.

In the illustrated embodiment, the switching pin 26 of the switching element 24 is slidably guided in the partial load rocker arm 14, wherein the stop 27 is disposed on the full-load rocker arm 13.

In contrast, it is also possible to arrange the stop 27 on the partial load rocker arm 14 and to guide the shift pin 26 of the switching element 24 displaceable in the full-load rocker arm 13 and to store.

Like also in Fig. 1 to 3 is shown, the part-load rocker arm 14 is rotated at its caused by the cam 17 rotation about the lever axis 18 against the bias of a return element 29.

The cams 15 and 17 of the valve train 10 have a defined contour. Thus, the first cam 15, which serves to actuate the Volllastschwinghebels 13 via the first roller 19, and the second cam 17, which serves to actuate the part-load rocker arm 14 via the second roller 20, over identical cam base circles 30. The first cam 15 has a relative to the base circle 30 radially outwardly projecting first cam projection 31 and the second cam 17 has a relation to the cam base circle 30 radially outwardly projecting second cam projection 32, wherein starting points 33, 34 of the two cam projections 31, 32 with respect to the respective cam base circle 30 in lie approximately at the same circumferential position.

Viewed in the direction of rotation D of the cams 15, 17 is an end point 35 of the cam projection 31 of the first cam 15 in front of an end point 36 of the second cam projection 32 of the second cam 17. About the second cam projection 32 of the second cam 17, which the actuation of the valve stem 11 in Accordingly, a longer valve opening time of the intake valves of the respective cylinder actuated by the valve drive 10 is adjustable.

In addition to the cam projection 32, the second cam 17 has a cam contour 37 recessed radially inward relative to the cam base circle 30. This cam contour 37 serves for the defined displacement of the switching pin 26 on the one hand in the activated state of the switching element 24 in an extension direction of the switching pin 26 in the coupling of FIG Part load rocker arm 14 and Volllastschwinghebel 13 and on the other hand in the inactivated state of the switching element 24 in a direction opposite to the retraction direction of retraction of the shift pin 26 in the separation of part load rocker arm 14 and Volllastschwinghebel 13th

The radially inwardly recessed cam contour 37 of the second cam 17 connects in the direction of rotation D of the cam 17 directly to the second projection 32 of the cam 17, wherein between the cam projection 32 and the cam contour 37 of the second cam 17, a smooth transition is ensured.

The displaceably guided shift pin 26 has a plurality of grooves positioned in the direction of displacement S one behind the other. In the illustrated embodiment, the shift pin 26 comprises two grooves 38 and 39, which are each designed as annular grooves. The shift pin 26 cooperates with the stop 27, according to Fig. 5 is provided by a blocking element 40, which is acted upon by a spring element 41.

Fig. 5 shows the shift pin 26 fragmentary in a fully retracted position in which the shift pin 26 the part-load swing lever 14 and the full load swing lever 13 from each other, in which case a front end 42 of the shift pin 26 seen in the extension of the shift pin 26 behind the locking element 40 and thus the Stop 27 is retracted.

Then, when the shift pin 26 of the switching element 24 is acted upon by hydraulic pressure and therefore activated, the switching pin 26, when the rollers 19, 20 roll on the cam base circle 30 of the respective cam 15, 17, with a free end 42 against the stop 27th pressed, wherein only when the roller 20 of the partial load rocker arm 14, the radially inwardly offset cam contour 37 of the cam 17 rolls over, the shift pin 26 can be displaced by lowering the same together with the part load rocker 14 under the stop 27 in the extension direction to the Part load rocker 14 and the full load rocker 13 to couple together.

Then, when the shift pin 26 is fully extended for coupling part-load swing lever 14 and full load swing lever 13, the spring-loaded locking element 40 and thus the stop 27 engages a first groove 39 of the shift pin 26 to lock the same in the fully extended position. If the shift pin 26 is to be shifted in the opposite direction to the retraction for the separation of partial load rocker 14 and Volllastschwinghebel 13, the switching element 24 is inactivated by withdrawing the hydraulic pressure, but in analogy to the extension of the shift pin 26 of the same can only be retracted if the roller 20 in turn rolls over the radially inwardly offset cam contour 37 of the cam 17 in order to lower the switching pin 26 relative to the stop 27 downwards, so that the same can then be retracted by the spring force of the spring element 28.

Then, when the building up of the hydraulic pressure for activating the switching element 24 or the removal of the hydraulic pressure for inactivation of the switching element 24 is so unfavorable that either when disconnecting part load lever 14 and full load rocker 13 of the shift pin 26 is not fully retracted or when coupling the part-load rocker 14 and full load rocker arm 13 of the shift pin 26 can not be fully extended, can by the second groove 38 which is positioned between the first groove 39 and the free end 41 of the shift pin 26, a critical overlap of the shift pin 26, the same effect a plastic deformation and thus damage can be avoided.

Both when extending the shift pin 26 and when retracting the same can therefore, if the stop 27 engages in the second groove 38, the shift pin 26 in a defined intermediate position, in which there is no risk of plastic component deformations are secured.

In subsequent, re-rolling the radially inwardly offset cam contour 37 of the cam 17 is the same released by lowering the shift pin 26 relative to the stop 27, so that the same starting from the defined intermediate position in its respective end position, ie when coupling part-load rocker arm 14 and full-load swing lever 13 in its fully extended end position and the separation of partial load rocker arm 14 and full load rocker arm 13 in its fully retracted position, can be moved.

Fig. 6 also shows the shift pin 26 in sections in a fully retracted position. Fig. 6 can be seen that such portions of the shift pin 26, which cooperate with the stop 27 and acted upon by the spring element 41 locking elements 40 in the fully retracted position of the shift pin 26 against a provided in the embodiment shown by the partial load rocker 14 bearing housing 43 for the shift pin 26 protrude.

In this respect, serve the portions of the shift pin 26, which cooperate with the stop 27 and are subject to damage during operation, not as bearing surfaces for mounting the shift pin 26 in the bearing housing 43. Accordingly, should an undesirable deformation of the shift pin 26 in the region of the sections done with the stop 27 act together, the shift pin 26 can still in the in Fig. 6 shifted completely retracted position. This is achieved by a relatively short design of the bearing housing 43.

This ensures that the cooperating with the stop 27 sections of the shift pin 26 protrude in the fully retracted position of the shift pin 26 relative to the bearing housing 43 and therefore do not form a sliding bearing surface for guiding the shift pin 26.

Another detail of the shift pin 26 of the valve gear according to the invention shows Fig. 7 , So shows Fig. 7 in that the switching pin 26 is assigned a projection 44 which, even in the fully retracted state of the switching pin 26, also protrudes for a defined distance of the switching pin 26 when it is extended into the hydraulic line 25, which serves to pressurize the switching pin 26 with hydraulic pressure. Only then, when the shift pin 26 is extended so far that the projection 44 is completely moved out of the hydraulic line 25, is in this case the full hydraulic effective surface of the shift pin 26 ready. In this respect, the full hydraulic power for hydraulic actuation of the shift pin 26 in the variant of Fig. 7 only available when the shift pin 26 is extended a defined distance. Thus, a pressure and speed controlled extension of the shift pin 26 can be realized.

With these details, it is possible to mechanically relieve the stop 27 or the locking element 40 acted upon by the spring element 41, in particular during the extension of the switching pin 26, because it is possible to ensure via the projection 44 that the full hydraulic pressure is only available when the free end 42 of the shift pin 26 has passed at least the right edge of the locking element 40. This prevents the hydraulic pressure acting on the shift pin 26 presses with full hydraulic force against the locking element 40 and thus possibly damage the same.

In order to allow a more rapid retraction when the shifting pin 26 is displaced in the opposite direction, namely during retraction, an additional discharge opening for hydraulic oil may be present in the region of the housing 43 of the switching pin 26. This additional, not shown in the figures discharge opening for the hydraulic oil allows faster retraction of the shift pin 26 in the separation of full load rocker arm 13 and part load rocker arm 14 and so a mechanical relief of the shift pin 26, such additional discharge opening is preferably hydraulically piloted.

When extending the shift pin 26, this additional discharge opening is closed, only when retracting the shift pin 26, the additional discharge opening is opened. This can be realized via a spring-loaded ball valve, which closes the additional discharge opening for extending the switching pin 26 and releases the same for retracting the switching pin 26.

LIST OF REFERENCE NUMBERS

10

valve train

11

tappet

12

tappet

13

Full load rocker

14

Partial load rocker

15

cam

16

camshaft

17

cam

18

lever axis

19

role

20

role

21

cam

22

role

23

rocker

24

switching element

25

hydraulic line

26

switching pin

27

attack

28

spring element

29

Return element

30

Cam base circle

31

cam lobe

32

cam lobe

33

starting point

34

starting point

35

endpoint

36

endpoint

37

cam contour

38

groove

39

groove

40

blocking element

41

spring element

42

The End

43

bearing housing

44

head Start

Claims (10)

Valve train for an internal combustion engine, in particular a marine diesel engine, with a full load rocker arm (13) for actuating a valve lifter (11) in a full load operating range of the internal combustion engine and with a part load rocker arm (14) for actuating the valve lifter (11) in a part load operating range of the internal combustion engine, wherein the full load rocker arm (13) by a first cam (15) of a camshaft (16) having a cam lobe radially outwardly projecting first cam projection (31) about a lever axis (18) is rotatable, and wherein the part-load rocking lever (14) by a a second cam (17) of the camshaft (16) having a second cam projection (31) projecting radially outward from a cam base circle, about which the lever axis (18) is rotatable; and a switching element (24) which in an inactivated state separates the partial load rocker arm (14) and the full load rocker arm (13) and which in an activated state couples the part load rocker arm (14) and the full load rocker arm (13) to each other, the 24) comprises a switching pin (26) and a stop (27), wherein the stop (27) either on Volllastschwinghebel (13) or the partial load rocker arm (14) is arranged, and wherein the switching pin (26) on the other, so either on Partial load rocking lever (14) or the Volllastschwinghebel (13) is guided displaceably in a thrust direction that the same in the activated state of the switching element (24) via the coupling of part load rocker arm (14) and Volllastschwinghebel (13) turning the Volllastschwinghebels (13) with the Partial load rocking lever (14) causes, characterized in that the second cam (17) of the camshaft (16) further one with respect to the respective cam base circle radially inwardly recessed cam contour (37) has to ensure the coupling and the separation of partial load rocker arm (14) and full load rocker arm (13) of a defined displacement of the shift pin (26). Valve gear according to claim 1, characterized in that a starting point (33) of the first cam projection (31) and a starting point (34) of the second cam projection (32) on the respective cam base circle (30) lie at the same circumferential position, and that in the direction of rotation of the cam seen an end point (26) of the second cam projection (32) behind an end point (35) of the first cam projection (31) lies on the respective cam base circle. Valve drive according to claim 1 or 2, characterized in that the radially inwardly recessed cam contour (37) of the second cam (17) seen in the direction of rotation of the second cam (17) can connect directly to the second cam projection (32) thereof. Valve gear according to one of claims 1 to 3, characterized in that the displaceably guided switching pin (26) has a plurality of the same successively positioned grooves (38, 39) in the displacement direction, which cooperate with a stop (27) forming, spring-loaded locking element (40) , Valve gear according to claim 4, characterized in that , when the shift pin (26) is fully retracted for separating part-load rocker arm and full-load rocker arm, a front end (42) of the same in the extension direction behind the locking element (40) is retracted, and then that when the shift pin (26) for coupling part-load swing lever and full load swing lever is fully extended, the front end (42) of the same seen in the extension direction in sections against locking element (40) is extended such that the locking element engages in the first groove (39) of the shift pin, said an intermediate position of the shift pin (26), the locking element (40) in second groove (38) which is disposed between the first groove (39) and the front end (42) of the shift pin engages. Valve gear according to claim 4 or 5, characterized in that the switching pin (26) in the full load rocking lever (13) is displaceably guided, and that the spring-loaded locking element (40) is arranged on the part-load rocking lever (14). Valve gear according to claim 4 or 5, characterized in that the switching pin (26) in the partial load rocker arm (14) is displaceably guided, and that the spring-loaded locking element (40) is arranged on Volllastschwinghebel (13). Valve gear according to one of claims 1 to 7, characterized in that the switching pin (26) of the switching element (24) via a hydraulic line (25) can be acted upon with hydraulic pressure, wherein the switching pin (26) with the hydraulic line (25) cooperating in such a projection (44) has that when it is extended in the activated state of the switching element (24) first a relatively small hydraulic pressure and then a relatively large hydraulic pressure at the switching pin (26) is effective. Valve drive according to one of claims 1 to 8, characterized in that those portions of the switching pin (26), which act together when displaced with the stop (27), in fully retracted position of the switching pin (26) relative to a bearing housing (43) of the Projecting shift pin (26). Internal combustion engine, in particular marine diesel engine, having a valve drive according to one of Claims 1 to 9.

Images