DE102008024876B4 - Valve drive for gas exchange valves of an internal combustion engine with displaceable cam carriers mounted on the front side - Google Patents

Abstract

Valve gear for gas exchange valves of an internal combustion engine, with at least one camshaft (4) and a plurality rotatably and axially displaceably guided on the camshaft (4), in stationary rotary bearings (17) rotatably mounted cam carriers (7), wherein each cam carrier (7) two at an axial distance mutually arranged cam pairs (8, 9) or cam groups, each cooperating with one of two gas exchange valves of a cylinder (3), wherein each pivot bearing (17) surrounds a front end (15, 16) of at least one of the cam carrier (7) and at least a part of the pivot bearings (17) surrounds two overlapping front ends (15, 16) of adjacent cam carriers (7), the front ends (15, 16) of the cam carriers (7) being tubular and coaxial with an axis of rotation (14) of the camshaft (4) are, characterized in that the two mutually facing front ends (15, 16) of adjacent cam carrier (7) in the manner of a telescopic tube engage with each other, wherein one of the two Front ends (15) has an outer diameter of the respective other of the two front ends (16) corresponding inner diameter and the inner diameter of the pivot bearing (17) corresponding outer diameter.

Description

The invention relates to a valve train for gas exchange valves of an internal combustion engine according to the preamble of claim 1.

To improve the thermodynamic properties of internal combustion engines valve trains are known in which the working cycle can be influenced, for example, to allow a speed-dependent change in the opening times or the stroke of the gas exchange valves.

From the DE 10 2004 011 586 A1 the applicant is already known a valve train of the type mentioned, in which a plurality of cam carrier rotatably and axially displaceably arranged on a base camshaft. For actuating two gas exchange valves of each cylinder of the internal combustion engine, two cam profile groups arranged at an axial distance from one another are provided on the associated cam carrier, each of which has two different cam profiles. By axial displacement of the cam carrier on the base camshaft between two displacement positions, one of the two cam profiles of each cam profile group can be brought into abutting contact with a roller of a roller cam follower of the associated gas exchange valve. In the known valve train, the cam carriers are rotatably mounted between the two cam profile groups in a rotary bearing of a camshaft bearing block of the cylinder head housing.

However, such a bearing of the cam carrier between its two cam profile groups encounters problems when the axial distance of the two associated with each cam carrier gas exchange valves is relatively small. In such a case, only a relatively small distance between the two cam profile groups is present, whereby either the axial displacement of the cam carrier is greatly limited by the bearing bridges or pivot bearings or only very narrow bearing bridges or pivot bearings can be used, which does not provide sufficient support Ensure camshaft or withstand high surface pressures.

Furthermore, the document is from the prior art DE 195 19 048 A1 known. This describes one in order to achieve different valve curves variable valve train, which contains several cams per adjustment, which can be adjusted axially or whose cam counter can be adjusted axially. There are facilities provided that lock the adjustment during the valve stroke, so that the adjustment takes place in the valve downtime.

Based on this, the present invention seeks to improve a valve train of the type mentioned in that it can also be used in internal combustion engines, in which the gas exchange valves to be actuated with the valve train of each cylinder have a small axial distance.

This object is achieved according to the invention with a valve drive for gas exchange valves of an internal combustion engine having the features of claim 1. It is provided that the two mutually facing front ends of adjacent cam carrier mesh in the manner of a telescopic tube, wherein one of the two end faces has an outer diameter of the other of the two front ends corresponding inner diameter and an inner diameter of the pivot bearing corresponding outer diameter.

With the combination of features according to the invention it is possible to use valve trains of the type mentioned also in such internal combustion engines, in which the two intake or exhaust valves of each cylinder have a small axial distance, since arranged at the front ends of the cam carrier pivot bearing by the distance of the two inlet or exhaust valves are not affected and thus can be formed wider than in a positioning between the two intake or exhaust valves. Since the cam carriers are further positioned on the camshaft so that their centers are located between the two intake or exhaust valves of the cylinders, the pivot bearings according to a preferred embodiment of the invention are no longer in the range between the intake or exhaust valves of the cylinders as before arranged on either side of these latter.

The invention provides that at least a part of the pivot bearing surrounds two overlapping front ends of adjacent cam carriers, the overlap of which may be more or less strong depending on the respective displacement position of the adjacent cam carriers.

In order to ensure a mutual overlap over the entire circumference of the cam carrier despite a mutual displacement of adjacent cam carrier with respect to each other, the cam carrier tubular, coaxial with the axis of rotation of the camshaft front ends, wherein the two mutually facing front ends of adjacent cam carrier in the manner of a telescopic tube interlock.

To provide for a mutual support of two intermeshing within a pivot bearing cam carrier front ends, has a the two tubular front ends on an outer diameter corresponding to the inner diameter of the pivot bearing, while its inner diameter corresponds to the outer diameter of the other of the two front ends. This ensures that when moving one of the two cam carrier in the region of the overlap on the one hand, the interlocking front ends slide and slides to the other one of the two ends on an inner cylindrical Lagerobefläche the pivot bearing, if this is advantageously designed as a sliding bearing whose Lagerobefläche cooperates with a cylindrical outer peripheral surface at the front end of a cam member.

While the pivot bearing for the cam carrier are displaced out of the center of the cam carrier out to their front ends, conversely, the means for axially displacing the cam carrier are instead arranged as before at the ends of the cam carrier preferably near the center of the cam carrier.

The same applies to means for locking each cam carrier in different displacement positions, which are also arranged at the cam carriers of known valve trains at the front ends of the cam carrier and are preferably arranged near the center in the cam carriers according to the invention.

• 1: eine Oberseitenansicht von Teilen eines Ventiltriebs für Paare von Einlassventilen von drei Zylindern eines 6-Zylinder-V-Motors mit mehreren auf einer Nockenwelle verschiebbaren, im Bereich ihrer Stirnenden gelagerten Nockenträgern;
• 2: eine horizontale Längsschnittansicht entlang einer Mittelachse der Nockenwelle;
• 3: eine vergrößerte Ansicht eines Abschnitts der Nockenwelle aus 2;
• 4: eine perspektivische Ansicht eines Teil des Ventiltriebs an einem Stirnende der Nockenwelle.

In the following the invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it:

• 1 FIG. 4 is a top view of parts of a valve train for intake valve pairs of three cylinders of a six-cylinder V-engine having a plurality of cam carriers slidable on a camshaft and mounted in the region of their front ends; FIG.
• 2 a horizontal longitudinal sectional view taken along a central axis of the camshaft;
• 3 : an enlarged view of a portion of the camshaft 2 ;
• 4 : A perspective view of a part of the valve train at a front end of the camshaft.

In the valve drive only partially shown in the drawing 1 1 for pairs of intake valves 2 ( 4 ) of three cylinders 3 a 6-cylinder diesel engine in V-construction with an overhead, in a cylinder head housing 5 ( 4 ) of the diesel engine rotatably mounted camshaft 4 let the hub and the opening times of the two of the camshaft 4 operated intake valves 2 every cylinder 3 adjust.

The valve train 1 includes for each cylinder 3 or for each pair of intake valves 2 a rotationally fixed and axially displaceable on the camshaft 4 mounted cam carrier 7 , as well as an actuator 6 ( 1 ) for moving the cam carrier 7 between two axially spaced defined shift positions.

The three hollow cylindrical cam carriers 7 have at their outer periphery in each case two axially spaced cam pairs 8th . 9 on, each of which consists of two cams 10 . 11 exists with different Hubkonturen. How best in 4 shown acts, each of the two cam pairs 8th . 9 with a roll 12 a pivotally mounted roller finger follower 13 the associated inlet valve 2 together. By an axial displacement of the cam carrier 7 can the role 12 as needed with one of the two cams 10 . 11 of the cam pair 8th or. 9 be brought into abutting contact so that they move during each revolution of the camshaft 4 once over a stroke contour of the cam 10 . 11 moved away while the roller rocker arm 13 under opening the inlet valve 2 pivoted. Due to different stroke contours of the two cams 10 . 11 can be the stroke and the opening time of each intake valve. 2 as a function of the displacement position of the cam carrier 7 regardless of the lift and the opening time of the intake valves 2 the other cylinder 3 be changed depending on the speed, for example.

The three cam carriers 7 each have an identical design and each have two tubular, to a rotation axis 14 the camshaft 6 coaxial front ends 15 . 16 ( 2 and 3 ), each in one of four plain bearings 17 protrude, which for rotatably supporting the cam carrier 7 and thus the camshaft 4 in the cylinder head housing 5 serve. In addition, there are two more plain bearings 18 provided in which the two opposite ends of the camshaft 4 are stored as best in 2 shown. All plain bearings 17 . 18 comprise two bearing half-shells bolted together, in the cylinder head housing 5 be mounted as best in 4 the example of two plain bearings 17 shown.

The tubular front ends 15 . 16 each cam carrier 7 are sized so that the outer diameter of one front end 15 the inner diameter of the associated plain bearing 17 corresponds, in which the front end 15 protrudes from one side, while the inner diameter of the front end 15 the outer diameter of the opposite front end 16 the same cam carrier 7 corresponds or the front end 16 of the adjacent cam carrier 7 from the opposite side into the plain bearing 17 protrudes. The facing ends 15 . 16 the two adjacent cam carrier 7 overlap within the slide bearing 17 in the manner of a telescopic tube, so that they are axially displaceable with respect to each other and slide on each other when moving. In this case, the respective radially outer front end is supported 15 directly on a cylindrical inner raceway of the sliding bearing 17 from, while the respective radially inner end 16 over the radially outer front end 15 of the adjacent cam carrier 7 indirectly on the running surface of the plain bearing 17 is supported.

How best in 3 shown, has the radially inner end face 16 each cam carrier 7 at its inner circumference a spline 20 on, which is still some way toward the middle of the cam carrier 7 extends and with a complementary external toothing 21 on the camshaft 4 combs to the cam carrier 7 rotatably and axially displaceable on the camshaft 4 respectively.

The axial displacement of a cam carrier 7 on the camshaft 4 in one of the two defined displacement positions for adjusting the stroke or the opening times of the associated intake valves 2 takes place if necessary and is always carried out when base circle sections of the cam pairs 8th . 9 the roles 12 the associated rocker arm 13 are opposite. To shift the actuator 6 of the cam carrier 7 actuated, the two adjacent drivers 22 ( 1 ), resulting from the actuator 6 extend. When operating the actuator 6 becomes one of the two drivers 22 when extending into a left- or right-handed helical groove 23 (see. 4 ) in the outer circumference of the cam carrier 7 meshed, the lane taker 22 in one of the two defined displacement positions is opposite to the cam carrier 7 during a subsequent revolution of the camshaft 4 as a result of the movement of the driver 22 through the helical groove 23 to move to the left or to the right in the other displacement position.

The distance between the two displacement positions corresponds to the center distance of the two cams 10 . 11 each cam pair 8th . 9 and the axial distance between two locking grooves 24 . 25 , which is roughly in the middle of each cam carrier 7 are omitted in its inner circumference. The two locking grooves 24 . 25 serve to lock the cam carrier 7 in the two defined displacement positions. The locking takes place by one in a transverse bore 26 the camshaft 4 arranged Arretierkugel 28 by the force of a helical compression spring 27 against a sloping flank 29 from one of the two locking grooves 24 . 25 pressed and thereby an axial force component in the cam carrier 7 is introduced to this against a serving as a stop face 30 an adjacent plain bearing 17 to press, as best in 3 shown.

LIST OF REFERENCE NUMBERS

1

valve train

2

intake valve

3

cylinder

4

camshaft

5

Cylinder head housing

6

actuator

7

cam support

8th

cam pair

9

cam pair

10

cam

11

cam

12

role

13

Roller cam

14

axis of rotation

15

tubular front end

16

tubular front end

17

Swivel bearing / plain bearing

18

Swivel bearing / plain bearing

20

spline

21

external teeth

22

takeaway

23

helical groove

24

locking groove

25

locking groove

26

cross hole

27

Helical compression spring

28

detent

29

oblique flank

30

face

Claims (8)

Valve gear for gas exchange valves of an internal combustion engine, with at least one camshaft (4) and a plurality rotatably and axially displaceably guided on the camshaft (4), in stationary rotary bearings (17) rotatably mounted cam carriers (7), wherein each cam carrier (7) two at an axial distance having mutually arranged cam pairs (8, 9) or cam groups, each with one of two Gas exchange valves of a cylinder (3) cooperate, wherein each pivot bearing (17) surrounds a front end (15, 16) of at least one of the cam carrier (7) and at least a portion of the rotary bearing (17) has two overlapping front ends (15, 16) of adjacent cam carrier (7) surrounds, wherein the front ends (15, 16) of the cam carrier (7) are tubular and to a rotational axis (14) of the camshaft (4) coaxial, characterized in that the two facing front ends (15, 16) of adjacent cam carrier (7) engage in the manner of a telescopic tube, wherein one of the two front ends (15) has an outer diameter of the respective other of the two front ends (16) corresponding inner diameter and the inner diameter of the pivot bearing (17) corresponding outer diameter. Valve gear after Claim 1 , characterized in that on either side of each cylinder (3) one of the rotary bearing (17) is arranged. Valve gear according to one of the preceding claims, characterized in that the pivot bearings (17) are designed as slide bearings (17) and have an inner cylindrical bearing surface which cooperates with a cylindrical outer peripheral surface at the front end (15) of a cam element (7). Valve gear after Claim 3 , characterized in that the sliding bearings (17) comprise two interconnected bearing half shells. Valve gear according to one of the preceding claims, characterized by means (6, 22, 23) for axially displacing the cam carrier (7). Valve drive according to one of the preceding claims, characterized by means (24, 25, 27, 28) for locking each cam carrier (7) in at least two different displacement positions. Valve gear according to one of the preceding claims, characterized by at least one further rotary bearing (18) in which a front end of the camshaft (4) is mounted. Internal combustion engine, characterized by at least one valve drive (1) according to one of the preceding claims.

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