EP2744987B1 - Camshaft for the valve train of an internal combustion engine - Google Patents

Description

The invention relates to a camshaft for the valve train of an internal combustion engine and an at least one such camshaft having internal combustion engine.

From the DE 10 2007 010 148 A1 a valve train of an internal combustion engine is known, which offers the possibility to adjust the stroke of the intake and exhaust valves of the internal combustion engine in stages. The adjusting device, which is designed so that it simultaneously adjusts the two intake and exhaust valves of each cylinder of the internal combustion engine, comprises a cam carrier as part of the camshaft, which is non-rotatably arranged in the axial direction displaceable on a basic shaft of the camshaft. The cam carrier has two cam groups, each with two (in the axial direction) arranged side by side cams with different cam shapes.

The adjusting device makes it possible to adjust the stroke of the valves associated with these cam groups in that the cam carrier is displaced into one of a total of three defined axial positions, whereby a contact element of a finger lever, with which the valves are actuated, either with one of the two cams or with a "Zero cam" is brought into contact, which is in principle a portion of the cam carrier, which has no cam lobe. Upon contact of the cam follower with one of the two cams, the respective valve is actuated with a stroke defined by the respective cam lobe and additionally dependent on the gear ratio of the cam follower. Upon contact of the rocker arm with the "zero cam", the stroke of the valve corresponding to the missing cam lift is zero. Accordingly, a valve shutdown is realized via the "zero cam".

An adjustment of the individual cam carrier in the axial direction of the camshaft is carried out by means of a respective guide wheel, which constitutes an integral part of the cam carrier. In the sliding gear a running in the circumferential direction, Y-shaped groove is intergrated. This groove thus has two divergent partial grooves in a section. The actual adjustment is achieved by means of an adjusting device, which has a total of three extendable adjusting pins, one of which, in each case Depending on the respective position of the cam carrier on the fundamental and the desired adjustment, is extended and engages in a portion of the groove. If one of the adjustment pins engages in one of the divergent sub-grooves, this leads to an axial displacement of the cam carrier on the basic shaft as a result of the relative rotation of the guide gear to the pin.

Between the two cam groups whose distance from each other by the distance of the actuated via these cam groups valves of the engine is defined in the valve train of the DE 10 2007 010 148 A1 a bearing ring is disposed rotatably disposed on the corresponding portion of the cam carrier. The bearing ring is rotatably but slidably disposed in the axial direction within a housing of the internal combustion engine, the cylinder head cover arranged. The bearing ring serves to support the camshaft in the cylinder head cover, wherein the displaceability of the cam carrier is made possible in the direction of the longitudinal axis of the camshaft.

The bearing ring forms on the outside a bar-shaped projection, which serves for a rotation of the bearing ring, whereby co-rotation is prevented with the camshaft. In addition, three recesses are integrated in the top of the bar-shaped projection, in which a ball of a spring-loaded locking element engages to fix the cam carrier in the respective position in which this has been adjusted by means of the guide wheel.

The bearing ring in the valve train of DE 10 2007 010 148 A1 consists of two half-shells, whereby an assembly on the limited by the cams of the two cam groups portion of the cam carrier is made possible. This embodiment of the bearing ring requires an extremely complex processing, since due to the high rotational speeds of the camshaft, which is rotatable relative to the bearing ring, very tight tolerances are required, a rotatory machining of the half shells is not possible. In addition, during assembly of the bearing ring a - albeit less - offset between the bearing halves can not be excluded, which would significantly increase the friction of the bearing ring on the corresponding portion of the cam carrier. Furthermore, the configuration of the bearing ring with the two bar-shaped projections has the disadvantage that the bearing of the bearing ring must be performed split in the cylinder head, which in the valve train of DE 10 2007 010 148 A1 is solved with the help of the cylinder head and a bolted bearing bracket. Such storage is expensive to install and thus increases the cost of the internal combustion engine.

Based on this prior art, the invention has the object, an improved internal combustion engine with a generic, from the DE 10 2007 010 148 A1 specify known valve train. In particular, the valve train should be improved so that the camshaft contained in this is easier to install and is characterized by a lower friction loss.

This object is achieved by a camshaft according to the independent claim 1 and by such a camshaft having internal combustion engine according to the independent claim 7. Advantageous embodiments of the camshaft or the internal combustion engine according to the invention are the subject of the dependent claims and will become apparent from the following description of the invention.

• eine Grundwelle,
• mindestens einen drehfest und axial verschiebbar auf der Grundwelle angeordneten Nockenträger, der mindestens eine Nockengruppe mit mindestens zwei in axialer Richtung nebeneinander angeordneten Nocken mit unterschiedlichen Nockenformen ausbildet, und
• mindestens einen drehbar und axial verschiebefest auf dem (bzw. jedem der) Nockenträger angeordneten Lagerring, der einstückig ausgebildet ist, derart weiterzubilden, dass der Lagerring in seiner Außenfläche eine (nicht senkrecht zur Längsachse des Lagerrings) verlaufende "Längsnut" und eine von dem Nutgrund zu der Innenseite des Lagerrings führende Bohrung aufweist.

According to the invention, a generic camshaft for the valve train of an internal combustion engine, the

• a fundamental wave,
• at least one rotatably and axially displaceably arranged on the fundamental shaft cam carrier which forms at least one cam group with at least two axially arranged side by side cams with different cam shapes, and
• at least one rotatably and axially displaceable on the (or each of) the cam carrier arranged bearing ring, which is integrally formed, such that the bearing ring in its outer surface (not perpendicular to the longitudinal axis of the bearing ring) extending "longitudinal groove" and one of the groove bottom has bore leading to the inside of the bearing ring.

The bearing of the bearing ring on the corresponding portion of the cam carrier is preferably formed as a hydrodynamic or hydrostatic sliding bearing. For this purpose it is provided that the bearing surfaces (i.e., the corresponding portion of the outer surface of the cam carrier and the inner surface of the bearing ring) via the bore in the bearing ring, a lubricant is supplied.

For this purpose, it is necessary to bring the bore into coincidence with a lubricant supply and this regardless of the respective axial displacement position of the bearing ring bearing cam carrier. Through the longitudinal groove, regardless of the respective axial adjustment position of the bearing ring, a connection to this Lubricant supply, which may be integrated, for example, in the housing of the internal combustion engine, be ensured.

As a "one-piece" according to the invention a bearing ring understood that is not composed of two or more sub-shells. Such a bearing ring may preferably also be designed in one piece, i. consist of only one component, of course, it is also possible to form a one-piece bearing ring according to the invention of a plurality of components, in which case at least the component that forms the inner surface is formed closed annular.

Due to the integral nature of the bearing ring whose manufacture is simplified because it can be manufactured as a simple turned part. In addition, can be achieved by the one-piece in a simple way a completely paragraph-free inside. Such an inside is in a bearing ring, which consists of two half-shells, as in the valve train in the DE 10 2007 010 148 A1 The case is not certainly avoidable, since an offset during assembly of the two half-shells can not be excluded. The one-piece bearing ring of the camshaft according to the invention is thus characterized in each case by a low friction of its rotational movement on the cam carrier.

As a "cam" of a camshaft according to the invention, a "zero cam" is understood according to the invention, which has no cam lobes and over which thus a zero stroke of the thus driven valve of the internal combustion engine is achieved.

An internal combustion engine according to the invention comprises at least one housing and at least one camshaft according to the invention arranged in the housing, wherein the basic shaft of the camshaft is rotatably supported within the housing via the at least one bearing ring of the cam carrier and the bearing ring is also displaceable relative to the housing in the axial direction of the camshaft ,

In order to allow a simultaneous adjustment of two or more valves of a cylinder of the internal combustion engine, (each) of the cam carrier of the camshaft according to the invention on a plurality and preferably two cam groups, which are arranged on both sides of the bearing ring.

In order to provide such a cam carrier according to the invention with a one-piece bearing ring, may preferably be provided that the cam carrier has a support tube, and at least one, preferably all of the cam groups (or. each formed by these cams) as structurally separate from the support tube, but with this (permanently) connectable or connected unit (s) are formed.

The formation of the cam carrier with a support tube and at least one, preferably a plurality of structurally separate cam groups not only has the advantage of mounting with a one-piece bearing ring according to the invention, but it is also possible to form the support ring and the cams (groups) of different materials in order to adapt them optimally to the different demands.

The cam carrier of the camshaft according to the invention preferably has a control ring with at least one control groove, which is introduced into its outer side and does not extend in at least one section in a radial plane of the camshaft. This creates the possibility of axially displacing the cam carrier on the fundamental shaft of the camshaft on the fundamental shaft by the temporary engagement of a control pin (not co-rotating with the camshaft) into the control groove.

Preferably, it can be provided that also the control ring is formed as structurally separate from the support tube, but with the support tube (permanently) connected component. As a result, if necessary, in turn, the assembly of the camshaft according to the invention can be simplified, but in any case there is the possibility to optimally adapt by a targeted selection of materials, the support tube or the control ring to the respective stresses.

For permanent connection of the cam group (s) and / or the control ring with the support tube, a press fit is preferably provided in which thus at the same component temperatures, the outer diameter of the (insulated) support tube slightly larger than the inner diameter of the (isolated) cam group (s) and / / or of the (isolated) Verschieberings, whereby these components are positively connected to each other in the joined state. In a known manner, the support tube is exposed to a lower temperature than the cam group (s) and / or the Verschiebering before assembly for the production of such a press fit; For this purpose, the support tube can be cooled and / or the cam group (s) and / or the sliding ring are heated. After cooling or reheating of the components after assembly then sets the desired interference fit.

The width of the longitudinal groove may have to correspond (at least) to the maximum displacement of the cam carrier on the fundamental shaft. This displacement may optionally be greater than the width of the bearing ring, which may be limited by the distance of the valves which are actuated by the cam groups of the cam carrier. This can complicate a constructive implementation of the lubricant supply, especially in small-volume internal combustion engines, since the integration of a sufficiently long longitudinal groove in the bearing ring does not seem feasible. In order to enable this in a constructive simple manner, it is provided in a preferred embodiment of the camshaft according to the invention that the outer diameter of the bearing ring is greater than the maximum cam lobe of the directly adjacent cams of the cam groups and the axial extent of the bearing ring - in at least a portion of its outer surface - greater than the distance between the two cam groups. As a result, the (maximum) width of the bearing ring over the distance of the two cam groups is extended in a simple manner.

An advantageous development of the internal combustion engine according to the invention provides that the bearing ring on the outside has a (further) longitudinal groove into which engages a non-rotatable with the camshaft, preferably fixed standing with respect to the housing fuse element to form a rotation of the bearing ring.

Furthermore, it can preferably be provided that the bearing ring on the outside forms at least two cavities spaced from one another in the axial direction of the camshaft, wherein a position assurance element not co-rotating with the camshaft, preferably fixed relative to the housing, depending on the respective axial position of the cam carrier on the camshaft engages in one of the recesses and thereby forms a position assurance or locking the cam carrier.

Because the longitudinal groove serving as anti-rotation lock and / or the depressions serving as position securing do not protrude beyond the outer surface of the bearing ring, a bearing of the bearing rings or the entire camshaft is made possible in an undivided bearing tunnel of the housing of the internal combustion engine. Thereby, the assembly of the internal combustion engine can be simplified.

Fig. 1:

einen Zylinderkopf einer erfindungsgemäßen Brennkraftmaschine;

Fig. 2:

die zwei Nockenwellen der erfindungsgemäßen Brennkraftmaschine gemäß der Fig. 1 vor der Montage in der Zylinderkopfhaube des Zylinderkopfs;

Fig. 3:

einen Abschnitt einer der Nockenwellen der Fig. 2;

Fig. 4:

die Bestandteile eines Nockenträgers der Nockenwellen gemäß Fig. 2;

Fig. 5:

einen Längsschnitt durch den Nockenträger gemäß Fig. 4;

Fig. 6:

den Nockenträger gemäß Fig. 4 und 5 in einer isometrischen Ansicht; und

Fig. 7:

einen Längsschnitt durch einen Abschnitt des Zylinderkopfs gemäß Fig. 1.

The invention will be explained in more detail with reference to an embodiment shown in the drawings. In the drawings shows

Fig. 1:

a cylinder head of an internal combustion engine according to the invention;

Fig. 2:

the two camshafts of the internal combustion engine according to the invention according to the Fig. 1 before mounting in the cylinder head cover of the cylinder head;

3:

a section of one of the camshafts of Fig. 2 ;

4:

the components of a cam carrier according to the camshaft Fig. 2 ;

Fig. 5:

a longitudinal section through the cam carrier according to Fig. 4 ;

Fig. 6:

according to the cam carrier Fig. 4 and 5 in an isometric view; and

Fig. 7:

a longitudinal section through a portion of the cylinder head according to Fig. 1 ,

The in the Fig. 1 and 2 illustrated cylinder head of an internal combustion engine according to the invention comprises a cylinder head cover 10 as part of a housing of the internal combustion engine. The cylinder head cover 10 forms two storage tunnels 12, in each of which a camshaft 14, 16 according to the invention is mounted. The two camshafts 14, 16 are driven by a crankshaft (not shown) of the internal combustion engine, to which a first of the camshafts 14 is connected to a drive wheel 18 which is connected via a toothed belt, not shown, with a corresponding output gear of the crankshaft. The first camshaft 14 drives the second camshaft 16 via a gearwheel drive, not shown. In this case, the second camshaft 16 may be provided with a phaser (not shown) via which a phase shift of the mutually coupled rotational movements of the two camshafts 14, 16 can be achieved.

Each of the two camshafts 14, 16 comprises a basic shaft 20, on which a total of four cam supports 22 are arranged secured against rotation. The anti-rotation is achieved via a spline on an inner surface of each of the cam carrier (see. Fig. 6 ) in connection with a corresponding longitudinal toothing on the outer surface of the respective section of the fundamental shaft 20. The longitudinal toothing ensures the inventively provided displaceability of the cam carrier 22 in the longitudinal direction of the camshaft 14, whereby a Hubumschaltung of the cam of the Cam carrier 22 actuated valves (not shown) of the internal combustion engine can be realized.

Each of the cam supports 22 comprises a support tube 24 and two cam groups 26 structurally separate from the support tube and formed as annular units, each of the cam groups 26 being divided in the axial direction into three adjacent sections. In two of these sections, the cam groups each form a cam, which rises from the cylindrical basic shape of the outer surface at one point of the circumference. The two cams of each of the cam groups 26 have different shapes and in particular different maximum elevations, resulting in different valve lifts for the valves operated therewith. The third section of each of the cam groups 26 has no elevations and represents a zero cam. The zero cam can be used to keep the "actuated" valve closed.

About the camshaft 14 according to the invention, a three-stage Ventilhubschaltung can be achieved. This Ventilhubschaltung is achieved via an axial displacement of the four cam carrier 22 per camshaft 14, wherein in each case an actuating element (not shown), such as a drag lever associated with each of the valves, in contact with one of the cam and the zero cam each the cam groups 26 is brought, whereby the valve is operated or not operated according to the shape of the respective cam or null cam.

The displacement of each of the cam carrier 26 via a control ring 28, in the rest of the cylindrical outer surface, a Y-shaped cam groove 30 is introduced. A first section of this control groove 30 extends exactly in the circumferential direction, ie in a (radial) plane arranged perpendicular to the longitudinal axis of the control ring 28. At this first section, a second section connects, in which the control groove 30 is formed of two diverging extending part-grooves. The control ring 28 of each of the cam supports 26 is associated with an actuator 32 connected to the cylinder head cover 10 having three control pins (not shown) which may be extended (individually driven) to engage the first portion or one of the sub-grooves of the second portion Control groove 30 of the associated control ring 28 engage and move the cam carrier 22 in one direction on the fundamental shaft 20 due to the relative movement between the rotating control ring 28 and the fixed control pin.

Furthermore, each of the cam carriers 22 comprises a bearing ring 34, which is rotatably arranged on the carrier tube 24 of the cam carrier 22 and between the two cam groups 26. The bearing ring 34 serves to support the camshaft 14 within the cylinder head cover 10. Since an axial displacement of the cam carrier 22 on the basic shaft 20 of the camshaft 14 and a corresponding displacement of the bearing ring 34 is required, the bearing of the bearing ring 34 in the cylinder head cover 10 before a corresponding axial displacement. For this purpose, the bearing ring 34 has an outer bearing shell 36, which is mounted displaceably in a section of the cylinder head cover 10 (in the longitudinal direction of the bearing ring or the camshaft). The outer bearing shell 36 has a cylindrical basic shape with a plurality of apertures, so that there is no completely closed cylindrical lateral surface. Furthermore, the bearing ring 34 still has a cylindrical inner bearing shell 38, which are connected to the outer bearing shell 36 via an annular web 40. The inner bearing shell 38 is supported on both sides on the two cam groups 26 of the cam carrier 22. The bearing ring 24 is in one piece according to the invention and also formed in one piece.

From the Fig. 3 It can be seen that the outer diameter of the outer bearing shell 26 is greater than the maximum elevation of the directly adjacent cams of the two cam groups 26. Furthermore, the outer bearing shell 36 projects beyond the inner bearing shell 38 in the axial direction and thus partially engages over the adjacent cams. As a result, the bearing ring 34 can be realized with an outer bearing shell 36, which is wider than the distance between the two cam groups 26 of the cam carrier 22 (limited by the distance between the two valves controlled by the respective cam carrier 22). This makes it possible to integrate a longitudinal groove 42 with a sufficient length in the outer bearing shell 36. This longitudinal groove 42 serves to establish a connection between a bore 44 extending from the groove base and extending through the web 40 to the inside of the inner bearing shell 38 and an outlet 46 of a lubricant supply integrated in the cylinder crankcase 10 (cf. Fig. 6 ).

In the outer bearing shell 36 of the bearing ring 34 is another (fully extending through the outer bearing shell 36) longitudinal groove 48 is integrated, into which engages a bolt of a screwed into the cylinder head 10 locking pin 50. About this locking pin 50, a rotation for the bearing ring 34 of each of the cam carrier 22 is realized without hindering its axial displacement.

In the outer bearing shell 36 of the bearing ring 34 are still three axially juxtaposed, wedge-shaped recesses 52 is introduced into which a spring-loaded ball 54 of a position assurance element 56 can engage. These three recesses 52 define axial positions in which the cam carrier 22 can be fixed by means of the position securing element 56.

The individual elements of the cam carrier (carrier tube 24, cam groups 26, bearing ring 34 and control ring 28) are connected by means of press fit. Their assembly is carried out as follows: The cam groups 26, the bearing ring 34 and the control ring 28 are pre-positioned and heated in the order provided. The carrier tube 24 is cooled simultaneously with liquid nitrogen. The cam groups 26, the bearing ring 34 and the control ring 2 are then inserted into a mounting device (not shown) and the support tube 34 then pushed through these elements. Then, the cam groups 26 and the bearing ring 34 and the control ring 28 in the intended positions (relative to each other) are rotated. After an approximation of the temperatures of the elements, the desired interference fit is formed.

LIST OF REFERENCE NUMBERS

10

Cylinder head cover

12

storage tunnels

14

first camshaft

16

second camshaft

18

drive wheel

20

fundamental wave

22

cam support

24

support tube

26

cam group

28

control ring

30

control groove

32

actuator

34

bearing ring

36

outer bearing shell

38

inner bearing shell

40

web

42

longitudinal groove

44

drilling

46

outlet

48

longitudinal groove

50

safety pin

52

deepening

54

Bullet

56

Position securing element

Claims (8)

1. Camshaft (14, 16) for the valve gear of an internal combustion engine having a basic shaft (20), at least one cam carrier (22) which is arranged on the basic shaft (20) axially displaceably and fixedly so as to rotate with it, the cam carrier (22) forming at least one cam group (26) with at least two cams which are arranged next to one another in the axial direction and have different cam shapes, and a bearing ring (34) which is configured in one piece and is arranged on the cam carrier such that it can be rotated and is fixed axially against displacement, characterized in that, in the outer face, the bearing ring (34) has a longitudinal groove (42) and a bore (44) which leads from a bottom of the longitudinal groove (42) to the inner side of the bearing ring (34).
2. Camshaft according to Claim 1, the cam carrier (22) having two cam groups (26) which are arranged on both sides of the bearing ring (34), characterized in that the cam carrier (22) has a carrier tube (24), and at least one of the cam groups (26) is configured as a unit which is structurally separate from the carrier tube (24) and is connected to the carrier tube (24).
3. Camshaft according to Claim 1 or 2, the cam carrier (22) having a control ring (28) with at least one control groove (30) which is made in an outer face of the control ring (28) and does not run in a radial plane of the camshaft at least in one section, characterized in that the control ring (28) is configured as a component which is structurally separate from the carrier tube (24) and is connected to the carrier tube (24).
4. Camshaft according to Claim 2 or 3, characterized in that the cam group/groups (26) and/or the control ring (28) is/are connected to the carrier tube (24) via a press fit.
5. Camshaft according to one of Claims 2 to 4, characterized in that the external diameter of the bearing ring (34) is greater than the maximum cam elevation of the directly adjacent cams of the cam groups (26), and the axial extent of the bearing ring (34) is greater in at least one section of its outer face than the spacing between the two cam groups (26).
6. Internal combustion engine having a housing and at least one camshaft (14, 16) according to one of the preceding claims which is arranged in the housing, the basic shaft (20) being mounted rotatably within the housing by means of the bearing ring (34), and the bearing ring (34) being displaceable relative to the housing in the axial direction of the camshaft (14, 16).
7. Internal combustion engine according to Claim 6, characterized in that the bearing ring (34) has a longitudinal groove (48) on the outer side, into which longitudinal groove (48) a securing element which is connected to the housing engages in order to secure the bearing ring (34) against rotation.
8. Internal combustion engine according to Claim 6 or 7, characterized in that, on the outer side, the bearing ring (34) has at least two depressions (52) which are arranged spaced apart from one another in the axial direction of the camshaft (14, 16), a positional securing element (56) which is connected to the housing engaging into one of the depressions (52) depending on the respective axial position of the cam carrier (22) on the camshaft (14, 16).

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