DE102010013216B4 - Valve train of an internal combustion engine - Google Patents

Abstract

Valve drive (1, 1') of an internal combustion engine with stroke-variable gas exchange valve actuation, comprising a camshaft (2, 2') with a support shaft (3) and a cam piece (4, 4') arranged thereon in a rotationally fixed manner and displaceable between axial positions, which has a cam group immediately adjacent to it Cams (14a, 14b, 14c, 15a, 15b, 15c) with different elevations and a groove-shaped axial link (16, 16') with two link tracks (20, 21, 20', 21') running in opposite axial directions, and two actuating elements ( 18, 19) which are axially stationary with respect to the camshaft (2, 2') and displaceable radially towards the camshaft (2, 2') in the internal combustion engine and for the purpose of moving the cam piece (4, 4') in the axial link (16 , 16') can be coupled in, the cam piece (4, 4') being provided with a bearing journal (12, 13 or 12') on which the camshaft (2, 2') rests in a camshaft bearing point (9, 10 or 9 ') of the internal combustion engine is mounted radially, thereby ken nshows that the axial link (16, 16') is designed to overlap axially with the camshaft bearing point (9, 9') on the bearing journal (12, 12'), the actuating elements (18, 19) being located in the camshaft bearing point (9, 9') get lost.

Description

field of invention

The invention relates to a valve drive of an internal combustion engine with variable-stroke gas exchange valve actuation, comprising a camshaft with a carrier shaft and a cam piece arranged thereon in a rotationally fixed manner and displaceable between axial positions, which cam piece has a cam group of directly adjacent cams with different elevations and a groove-shaped axial link with two link tracks running in opposite axial directions, and two actuating elements which are arranged in the internal combustion engine so as to be axially stationary with respect to the camshaft and displaceable radially in relation to the camshaft and which can be coupled into the axial link for the purpose of displacing the cam piece, the cam piece being provided with a bearing journal on which the camshaft is radially mounted in a camshaft bearing point of the internal combustion engine is stored.

Background of the Invention

The lift variability of such a valve train is known to be based on a cam piece with cams arranged immediately adjacent thereto, the different elevations of which are selectively transmitted to a gas exchange valve by means of a conventionally rigid cam follower. For activation of the respective elevation depending on the operating point, the cam piece is non-rotatably, but displaceably arranged on a carrier shaft between two or more axial positions and has link tracks running in opposite directions in the axial direction in the form of spiral grooves. Depending on the design of the link tracks, the cam piece is displaced via one or more actuating elements which are coupled alternately into the spiral grooves. The axial course of the spiral groove in engagement with the actuating element causes the cam piece to shift from one axial position to the next in a self-controlled manner and camshaft angle-preserving during the common (elevation-free) base circle phase of the cams of a cam group. The radial course of a spiral groove is usually designed in such a way that it becomes increasingly flatter towards the end of the displacement process and pushes back the actuating element which is currently engaged into its non-engaging rest position.

A generic valve train with two-stage stroke variability is, among other things, from the DE 101 48 179 A1 out. An essential property of this valve train is that the individual cam pieces are provided with bearing journals, which are mounted so as to slide both radially and axially in associated camshaft bearing points of the internal combustion engine. In contrast, the camshaft bearing is in DE 101 48 177 A1 and DE 10 2004 022 832 A1 disclosed valve trains directly on the support shafts. While in this case the length of a cam piece is largely determined by the number of cams and link tracks and their spatial arrangement relative to one another, the length of the bearing pin or, if applicable, the bearing pin must also be taken into account in the first case. However, taking into account various design parameters of the internal combustion engine, in particular the cylinder and gas exchange valve spacing, the number and width of the cams and the central or end camshaft bearing position in relation to a cylinder, the required length of the cam piece quickly collides with the space available for it. This applies to a greater extent with three-stage stroke variability.

object of the invention

The present invention is therefore based on the object of developing a valve train of the type mentioned at the outset in such a way that the cam piece is designed to be as compact as possible axially, so that not only can the valve train be used widely, even in small-volume internal combustion engines, but there is also great potential for more are given as a two-stage, in particular three-stage stroke variability.

Summary of the Invention

The solution to this problem results from the characterizing features of claim 1, while advantageous developments and refinements of the invention can be found in the dependent claims. Accordingly, the axial link is designed to overlap axially with the camshaft bearing on the bearing journal, with the actuating elements running in the camshaft bearing. In other words, the idea on which the invention is based is to eliminate the spatial separation of the bearing journal and axial link and to "merge" them axially with one another in order to correspondingly reduce the axial installation space of the cam piece and/or to provide the cam group with an additional cam be able.

With regard to the stability and fatigue strength of the camshaft bearing, which of course still has to be guaranteed, it is provided in a further development of the invention that the bearing journal forms a plain bearing with the camshaft bearing point, the bearing journal having sliding surface sections axially on both sides of the axial link.

In addition, the bearing diameter of the bearing journal should be larger than the enveloping circle diameter of the cam closest to the bearing journal, this cam and the camshaft bearing point overlapping axially in one of the axial positions of the cam piece. The immersion of the cam group in the camshaft bearing point made possible in this way is particularly useful or even necessary if the cam piece has two cam groups for actuating two gas exchange valves, which are arranged at a small distance from the camshaft bearing point, and if a three-stage lift variability with three cams per cam group is also provided is.

With regard to the bearing arrangement of the camshaft, the cam piece should have two bearing journals formed at the axial end portions thereof and two cam groups arranged between the bearing journals. This bearing arrangement correlates with camshaft bearing points which are arranged between the cylinders of an internal combustion engine with multi-valve technology. On both bearing journals, unidirectionally acting axial linkages can be fitted with a single slideway according to the one cited at the outset DE 101 48 179 A1 be provided, in which extending in both associated camshaft bearing points actuating elements can be coupled.

In an alternative embodiment of the invention, the cam piece should have two cam groups formed on its axial end sections and only one bearing journal arranged between the cam groups. This bearing arrangement correlates with camshaft bearing points which are arranged between the gas exchange valves of a cylinder of an internal combustion engine with multi-valve technology.

In addition, it is provided that the cam piece has exactly one axial link, which is configured bidirectionally with two link tracks running in opposite directions axially. An embodiment of such an axial link is already from the initially cited DE 101 48 177 A1 previously known: here the two link tracks are arranged next to one another in the circumferential direction of the bearing journal and intersect in the middle. The main advantage compared to the spatially separate, unidirectional link tracks is, on the one hand, the comparatively small amount of axial space required for the axial link and, on the other hand, that a single actuating element is sufficient for both displacement directions.

This also applies to a bidirectional axial link according to an alternative second embodiment. In this case, the two link tracks should be arranged one behind the other in the circumferential direction of the bearing pin, with the starting point of one link track adjoining the end point of the other link track. The kinematics of such an axial link goes in detail from the unpublished DE 10 2009 009 080 A1 out.

In addition, the two aforesaid configurations allow the stroke variability to be increased from two to three stages in a comparatively simple manner, in that two actuating elements are coupled alternately into the bidirectional axial links. This is in the also not pre-published DE 10 2007 051 739 A1 disclosed in more detail for the design with intersecting link tracks.

In the case of the three-stage lift variability, it is provided that one of the three cams of a cam group is free of elevations. This cam is a so-called base circle cam which, due to its purely cylindrical shape, leads to the deactivation of the gas exchange valve.

If possible and expedient, the aforementioned features and configurations of the invention should also be able to be combined with one another as desired.

character list

• 1 einen Ausschnitt eines Zylinderkopfs einer Brennkraftmaschine mit einer ersten Ausführung eines erfindungsgemäßen Ventiltriebs in perspektivischer Zusammenbaudarstellung;
• 2 den Ausschnitt aus 1 ohne Nockenwellenlagerdeckel;
• 3 den Ausschnitt gemäß den 1 und 2 in perspektivischer Längsschnittdarstellung;
• 4 die Axialkulisse gemäß den 1 bis 3 in einer ersten perspektivischen Ansicht;
• 5 die Axialkulisse gemäß 4 in einer zweiten (ca. 180° gedrehten) perspektivischen Ansicht;
• 6 einen Ausschnitt eines Zylinderkopfs einer Brennkraftmaschine mit einer zweiten Ausführung eines erfindungsgemäßen Ventiltriebs in perspektivischer Zusammenbaudarstellung;
• 7 den Ausschnitt aus 6 ohne Nockenwellenlagerdeckel;
• 8 das Nockenstück gemäß den 6 und 7 als perspektivische Einzelteildarstellung;
• 9 die Axialkulisse gemäß den 6 bis 8 in einer ersten perspektivischen Ansicht;
• 10 die Axialkulisse gemäß 9 in einer zweiten (ca. 120° gedrehten) perspektivischen Ansicht und
• 11 die Axialkulisse gemäß 9 in einer dritten (ca. 240° gedrehten) perspektivischen Ansicht.

Further features of the invention result from the following description and from the drawings, in which exemplary embodiments of the invention are shown in a partially simplified manner. Unless otherwise mentioned, features or components that are the same or have the same function are provided with the same reference numbers. Show it:

• 1 a section of a cylinder head of an internal combustion engine with a first embodiment of a valve train according to the invention in a perspective assembly view;
• 2 the cutout 1 without camshaft bearing cap;
• 3 the section according to the 1 and 2 in a perspective longitudinal section;
• 4 the axial link according to the 1 until 3 in a first perspective view;
• 5 according to the axial link 4 in a second perspective view (rotated by about 180°);
• 6 a section of a cylinder head of an internal combustion engine with a second embodiment of a valve train according to the invention in a perspective assembly view;
• 7 the cutout 6 without camshaft bearing cap;
• 8th the cam piece according to the 6 and 7 as a perspective detail view;
• 9 the axial link according to the 6 until 8th in a first perspective view;
• 10 according to the axial link 9 in a second (approx. 120° rotated) perspective view and
• 11 according to the axial link 9 in a third (approx. 240° rotated) perspective view.

Detailed description of the drawings

In the 1 until 3 discloses a section of a valve train 1 of an internal combustion engine with variable-stroke gas exchange valve actuation and four-valve technology that is essential for understanding the invention. A central component for the function of the valve train 1 is a camshaft 2, which includes a carrier shaft 3 and--corresponding to the number of cylinders of the internal combustion engine--rotatably mounted thereon and displaceable between three axial positions. For the purpose of axial displacement, the carrier shaft 3 is provided with an external spline 5 and each cam piece 4 is provided with a corresponding internal spline 6 . The known gears are in the 3 and 8th recognizable. The discernible gaps between the axial end sections 7 and 8 of the cam pieces 4 allow the cam pieces 4 to be displaced separately and synchronously with the ignition sequence of the internal combustion engine into a respective adjacent axial position. The camshaft 2 is radially supported in camshaft bearing points 9 and 10, which in this exemplary embodiment are arranged between the cylinders of the internal combustion engine. The rocker arms 11, which can be seen between the camshaft bearing points 9, 10, actuate the two intake valves of a cylinder, not shown here.

How out 2 - the same section is shown as in 1 , but without the upper camshaft bearing cap - the cam piece 4 is provided at its end sections 7, 8 with bearing journals 12 and 13 of different widths, which are mounted so as to slide both radially and axially on the inner lateral surfaces of the camshaft bearing points 9, 10. Groups of cams running between the bearing journals 12, 13 each consist of three immediately adjacent cams 14a, 14b and 14c and 15a, 15b and 15c, which have different elevations with the same base circle radius. These are selectively, ie depending on the instantaneous axial position of the cam piece 4, transferred to the gas exchange valves by means of the rocker arms 11. The different elevations mean different amounts of the respective cam lift and/or different valve control times of the cams 14a, 14b and 14c as well as 15a, 15b and 15c. The cams 14a and 15a are so-called base circle cams, which are free of elevations and each lead to the deactivation of the gas exchange valve.

The displacement of the cam piece 4 between its axial positions takes place outside the elevations during the common base circle angle of the cams 14a, 14b and 14c and 15a, 15b and 15c. That, for example, from the initially cited DE 101 48 179 A1 The fundamentally known functional principle of the actuator system required for this is based on a groove-shaped axial link 16 on the cam piece 4 and an actuating element in the form of a cylindrical actuator pin, which is axially stationary with respect to the camshaft 2 but can be displaced radially towards the camshaft 2 in the internal combustion engine and is arranged in the internal combustion engine for the purpose of displacing the cam piece 4 can be coupled into the axial link 16 .

The presently used actuator 17 in the 1 and 2 is only recognizable from the obscured, goes closer from the lengthwise section in 3 out. The actuator 17 comprises two actuator pins 18 and 19 spaced apart by a cam width, which are selectively driven out of a common actuator housing by means of an electromagnetically actuated locking mechanism and are alternately coupled into the single axial link 16 for each cam piece 4 . The structural design of this actuator 17 is in detail from the unpublished DE 10 2009 010 949 A1 out.

The in the 4 and 5 The axial link 16 shown as a detail from two opposite perspectives is designed with two link tracks 20 and 21 running in opposite axial directions, with the two link tracks 20, 21 being arranged next to one another in the circumferential direction and crossing in the middle. While such an axial link 16 is known in principle, the link tracks 20, 21 in the present exemplary embodiment are offset in height radially relative to one another in order to produce forced guidance of the coupled-in actuator pin 18 or 19 on both sides along the radially lower link track 20. In this way, even when the camshaft speed is low and the axial mass inertia of the cam piece 4 is correspondingly low, its displacement process along the radially lower link path 20 can be completed completely after the crossing point has been passed.

Regarding the way the actuators work: Coupling the actuator pin 18 into the link track 20 causes the cam piece 4 to shift to the left (in 3 ) and - starting from that shown axial position, in which the rocker arms 11 are acted upon by the central cams 14b and 15b - to activate the cams 14c and 15c. Conversely, when the actuator pin 19 is coupled into the link track 21, the cam piece 4 is displaced to the right and--starting from the axial position shown--the cams 14a and 15a are activated. Coupling the same actuator pin 18 or 19 twice in immediate succession results in a back and forth displacement of the cam piece 4 into the original axial position. On the other hand, an immediately successive, alternating coupling of the actuator pins 18 and 19 into the same link track 20 or 21 leads to a rectified displacement of the cam piece 4 by two axial positions. Thus, only an actuator 17 with the two actuator pins 18, 19 and an axial link 16 are required to set the three axial positions of the cam piece 4.

The cam piece 4 is secured in its respective axial position by a locking device against uncontrolled displacement. The locking device, which is known per se and not shown in detail here, comprises a spring-loaded pressure piece 22, which is mounted in a transverse bore 23 in the carrier shaft 3 and - depending on the axial position of the cam piece 4 - in one of three circumferential grooves 24, 25 and 26 on the inner circumference of the cam piece 4 snaps.

According to the invention, the actuator 17 runs within the axial longitudinal extent of the camshaft bearing point 9. This means that its inner lateral surface is cut by a bore hole for receiving the actuator 17 and accordingly the axial link 16 formed on the circumference of the bearing journal 12 and the camshaft bearing point 9 overlap in the axial direction . Sliding surface sections 27 and 28 on both sides of the axial link 16 are used to form the plain bearing of the bearing journal 12 in the camshaft bearing point 9. The bearing journal 13 is significantly narrower and fully cylindrical than the bearing journal 12 with the axial link 16 running thereon.

An alternative embodiment of a variable-stroke valve train 1 'is from the 6 until 8th emerges, whereby the following explanations are largely limited to the structural differences to the valve train 1. In the case of the valve train 1', the camshaft bearing points 9' are not between the cylinders but between the gas exchange valves 29 of a cylinder. Accordingly, the two cam groups with the cams 14a, 14b and 14c as well as 15a, 15b and 15c are arranged on the two end sections 7, 8 of the cam piece 4', which only has a bearing pin 12' running in between for the radial bearing of the camshaft 2' in the respective associated Camshaft bearing 9 'has. The one from the 1 until 3 known actuator 17 is accommodated in the upper camshaft bearing cap 30 in this case.

What both valve trains 1' and 1 have in common is that the gas exchange valves 29 and consequently also the rocker arms 11 run at a close distance from the camshaft bearing point(s) 9' or 9 and 10. The axial clearance of the cam groups relative to the camshaft bearing point 9' required for the three-stage lift variability is created in that, depending on the axial position of the cam piece 4', the cam groups dip into the camshaft bearing point 9' with their cams 14a and 15c closest to the bearing journal 12'. in the in 7 In the illustrated axial position of the cam piece 4', the gas exchange valves 29 are momentarily acted upon by the cams 14c and 15c, while the base circle cam 14a and the camshaft bearing point 9' overlap axially. The opposite axial position of the cam piece 4' with then effective base circle cams 14a and 15a also requires the cam 15c to dip into the camshaft bearing point 9'.

like it in 8th As can be seen, the axial clearance of the cam groups in relation to the camshaft bearing point 9' results from the fact that the bearing diameter of the bearing journal 12' is larger than the enveloping circle diameter 31 shown in dotted lines of the cam 15c closest to the bearing journal 12' and is also larger than the base circle diameter of the cam 14a. This geometric configuration applies to the cams 14c and 15a in a corresponding manner for the valve train 1 according to FIGS 1 until 5 to.

The axial link 16' formed on the circumference of the bearing journal 12' is also formed with two link tracks 20' and 21' running in opposite axial directions, acting bidirectionally and limited on both sides by the sliding surface sections 27, 28, which form a plain bearing with the camshaft bearing point 9'. Compared to the axial link 16, however, the link tracks 20', 21' are not arranged next to one another with the same starting and end points, but are arranged one behind the other in the circumferential direction of the bearing pin 12'. How it from the 9 until 11 with the axial link 16' rotated by approximately 120°, the starting point 32 of the link track 20' borders on the end point 33 of the link track 21', and the starting point 34 of the link track 21' borders on the end point 35 of the link track 20'. In this case too, two actuator pins 18, 19 spaced one cam width apart (see Fig 3 ) sufficient, which according to the previous explanation alternately in the same axial link 16 'einkop become pelted. Although the camshaft angle available for moving the cam piece 4' is significantly smaller compared to the axial link 16 with the crossing link tracks 20, 21, there is a significant advantage in the continuous positive guidance of the respectively coupled actuator pin 18 or 19, so that a safe shifting of the Cam piece 4' is possible even without its supporting inertia, ie at the lowest camshaft speeds.

Reference List

1

valve train

2

camshaft

3

carrier wave

4

cam piece

5

external splines

6

internal splines

7

axial end portion of the cam piece

8th

axial end portion of the cam piece

9

camshaft bearing point

10

camshaft bearing point

11

rocker arms

12

bearing journal

13

bearing journal

14

Cam group with cams 14a, 14b and 14c

15

Cam group with cams 15a, 15b and 15c

16

axial backdrop

17

actuator

18

Actuator pin / operating element

19

Actuator pin / operating element

20

slide track

21

slide track

22

Pressure piece

23

Cross bore of the carrier shaft

24

circumferential groove

25

circumferential groove

26

circumferential groove

27

sliding surface section

28

sliding surface section

29

gas exchange valve

30

camshaft bearing cap

31

enveloping circle diameter

32

Starting point of one slide track

33

End point of the other slide track

34

Starting point of the other slide track

35

End point of a slide track

Claims (4)

Valve drive (1, 1') of an internal combustion engine with stroke-variable gas exchange valve actuation, comprising a camshaft (2, 2') with a support shaft (3) and a cam piece (4, 4') arranged thereon in a rotationally fixed manner and displaceable between axial positions, which has a cam group immediately adjacent to it Cams (14a, 14b, 14c, 15a, 15b, 15c) with different elevations and a groove-shaped axial link (16, 16') with two link tracks (20, 21, 20', 21') running in opposite axial directions, and two actuating elements ( 18, 19) which are axially stationary with respect to the camshaft (2, 2') and displaceable radially towards the camshaft (2, 2') in the internal combustion engine and, for the purpose of moving the cam piece (4, 4') in the axial link (16 , 16') can be coupled in, the cam piece (4, 4') being provided with a bearing journal (12, 13 or 12') on which the camshaft (2, 2') rests in a camshaft bearing point (9, 10 or 9 ') of the internal combustion engine is mounted radially, thereby geke Characterized in that the axial guide (16, 16 ') with the camshaft bearing point (9, 9') is designed to overlap axially on the bearing journal (12, 12'), the actuating elements (18, 19) in the camshaft bearing point (9, 9') get lost. Valve train (1, 1 ') after claim 1 , characterized in that the bearing journal (12, 12') forms a sliding bearing with the camshaft bearing point (9, 9'), the bearing journal (12, 12') having sliding surface sections (27, 28 ) having. Valve train (1, 1 ') after claim 1 , characterized in that the bearing diameter of the bearing journal (12, 12') is greater than the enveloping circle diameter (31) of the cam (14c, 15a or 14a, 15c) closest to the bearing journal (12, 12'), this cam ( 14c, 15a or 14a, 15c) and the camshaft bearing point (9, 9') overlap axially in one of the axial positions of the cam piece (4, 4'). Valve train (1 ') after claim 1 , characterized in that the cam piece (4 ') has two at its axial end portions (7, 8) formed cam groups, wherein the bearing zap fen (12') is arranged between the cam groups.

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