DE102007027979B4 - Valve train for gas exchange valves of an internal combustion engine with camshaft tunnel bearings - Google Patents

Abstract

Valve gear for gas exchange valves of an internal combustion engine with a camshaft (1, 2), at least two rotatably and axially displaceable on the camshaft (1, 2) guided cam pieces (5) each having a radial bearing (15) for rotatably supporting the cam pieces (5) and the Camshaft (1, 2), and holders (23) for the radial bearing (15), in which the radial bearings (15) secured against rotation and axially displaceable, characterized in that the holders (23) integral with an upper part (3 ) are formed of a two-part cylinder head housing and serve as a seat for the two half-shells (20, 21) radial bearings (15) serving passage openings (24) in the radial direction on all sides, and that the radial bearings (15) have an outer diameter, the larger as the largest circle diameter of cams (8, 9, 10) of the cam pieces (5).

Description

The invention relates to a valve train for gas exchange valves of an internal combustion engine according to the preamble of claim 1 and an internal combustion engine having such a valve train according to claim 16.

To improve the thermodynamic properties of internal combustion engines mechanical devices are known which influence the working cycle of the valve train and, for example, allow a speed-dependent change in the opening times or the stroke of the gas exchange valves of cylinders of the internal combustion engine.

From the EP 1 608 849 B1 A valve train is already known, in which an intake camshaft and an exhaust camshaft are mounted in stationary bearings, wherein the bearings can be divided along a parting plane between a cylinder crankcase and a cylinder head housing. On the two camshafts each cam pieces are arranged rotationally fixed and axially displaceable. For actuating two inlet and outlet valves of a cylinder of the internal combustion engine two axially offset cam groups are provided on each cam piece, each having two cams with different cam profiles. By axial displacement of the cam piece between two displacement positions one of the two cams of each cam group can be brought into abutting contact with a cam follower of an adjacent valve, whereby the stroke and / or the opening times of this valve can be adjusted. The axial displacement of the cam piece on the camshaft is effected by means of two counter-rotating worm gears, which are arranged at an axial distance from each other in the cylinder head housing. Each worm gear has an actuator and a dog which can be engaged by operating the actuator with a left-handed or a right-handed helical groove on the cam piece to move the cam piece to the right or left. The cam piece is rotatably and axially displaceably mounted in a stationary bearing between the two cam profile groups. The DE 10 2004 011 586 A1 also discloses such a valvetrain.

Furthermore, from the document DE 103 31 089 A1 a cylinder head cover for an internal combustion engine with at least one camshaft known which protrudes through at least one bearing bridge along a bearing lane for the camshaft in the cylinder head cover, wherein the bearing bridge has an opening or bore which completely surrounds the camshaft.

To improve the influence on the working cycle of the valve train, it would be desirable to expand the cam groups by another cam with a different cam contour or a different cam profile. Such an extension of the cam groups by a further cam or a further cam profile, however, makes it necessary to move each cam piece between three different displacement positions back and forth, in which each other cam interacts with the cam follower. As a result, the displacement of the cam piece is longer, which can lead to problems in the axial dimensioning of the bearing in view of the relatively small axial distance between adjacent gas exchange valves of a cylinder, in particular in the case of storage of the cam piece between the valves.

In order to allow an enlargement of the displacement of the cam pieces was not previously published by the applicant in the DE 10 2007 010 149 A1 proposed to arrange the right-handed groove and the left-hand groove immediately adjacent to each other and to let Y-shape merge into each other.

Next was for the same purpose in the not pre-published DE 10 2007 010 148 A1 the Applicant already proposed a valve train of the type mentioned, in which the bearing for the camshaft or the cam pieces radial bearings are axially displaceable in receiving openings, which are formed by two serving as a holder split bearing bridges of the cylinder head housing and the cylinder crankcase.

However, the width of the bearings is still relatively low, so that on the one hand no unused cam pieces can be used, since these have a greater axial length than built cam pieces with embossed cam profiles due to the machining of a blank. On the other hand, the switching release, d. H. the remaining axial distance between two adjacent, located in opposite displacement positions cam pieces, not readily guaranteed at a required standard cam width.

Proceeding from this, the present invention seeks to eliminate the aforementioned problems in a valve train of the type mentioned in order to allow a larger bearing width and the use of uninstalled cam pieces.

This object is achieved according to a first variant of the invention in that the brackets are integrally formed with an upper part of a two-part cylinder head housing and completely surround passage or receiving openings for the radial bearings.

A preferred embodiment of the invention provides that the camshaft with the cam pieces and the radial bearings is axially inserted through a part of the passage or receiving openings in the integrally formed on the upper part of the cylinder head housing mounts, which together form an interrupted in the axial direction tunnel bearings in the upper part ,

According to the invention, the radial bearings have an outer diameter which is greater than the largest circle diameter of the cams, so that on the one hand the passage of the cam groups of the cam pieces through the passage or receiving openings of the brackets is not hindered and on the other hand, the one piece on the upper part of the Cylinder head housing molded brackets in the axial direction of the camshaft can be made relatively wide, thereby increasing the bearing width.

After insertion of the preassembled camshaft in the tunnel bearings, the radial bearings are preferably held in the brackets that they are on the one hand secured against rotation and on the other hand, together with the cam pieces between two end stops are axially displaceable. For this purpose, the holders each comprise at least one anti-rotation and / or stop element, which can expediently be inserted through a part of the holder into a recess of the radial bearing.

For mounting the radial bearing between two cam groups of a cam piece these are expediently designed as sliding bearings and consist of two half-shells, which are firmly connected to each other, for example by spring clips, screws or by an adhesive connection.

A preferred embodiment of the first variant of the invention provides that at least a portion of the cam pieces has a front-side recess surrounding the camshaft, in which an opposite end face of an adjacent cam piece is a piece of inserted.

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

1 FIG. 2 is a bottom perspective view of a cylinder head shell with an intake camshaft and an exhaust camshaft on each of which a plurality of cam pieces are axially slidably mounted; FIG.

2 FIG. 3 is a perspective view of one of the cam pieces mounted on the intake camshaft; FIG.

3 : another perspective view of the cam piece during assembly of a split radial bearing with means for locking the cam piece in different displacement positions;

4 a perspective view of the cam piece accordingly 3 but after assembly of the radial bearing and the locking means;

5 : A perspective view of the cam piece and the radial bearing when inserted into an associated tunnel section of a tunnel bearing of the cylinder head shell;

6 two side views of the cam piece and the radial bearing after insertion into the tunnel section in two different outer displacement positions;

7 a perspective end view of the cam piece and the radial bearing after insertion into the tunnel section;

8th : a perspective front view corresponding 7 but shown to illustrate the lubrication of the radial bearing partially transparent;

9 a longitudinal sectional view of the cam piece, the radial bearing and the tunnel portion and the locking means;

10 : a longitudinal sectional view corresponding 9 also showing part of an adjacent cam piece with the cam pieces in opposite sliding positions.

How best in 1 As shown, a valve train for the intake valves and the exhaust valves of cylinders of a 4-cylinder in-line engine includes an intake camshaft 1 and an exhaust camshaft 2 , which are in parallel alignment in the upper part 3 a cylinder head housing of the in-line motor are rotatably mounted and at its one end face a sprocket 4 for a chain drive, with which the camshafts 1 . 2 be driven by the crankshaft of the engine.

On the two overhead camshafts 1 respectively. 2 There are four cam pieces each 5 rotatably mounted and axially displaceable, with which the stroke and the opening times of the two inlet and outlet valves of each cylinder can be adjusted.

To the cam pieces 5 on the one hand rotatably with the associated camshaft 1 respectively. 2 on the other hand, however, their axial displacement along the camshaft 1 respectively. 2 allow to have the hollow cylindrical cam pieces 5 at their inner circumference a spline 6 on how best in 9 shown after the assembly of the cam pieces 5 with a complementary toothing (not shown) on the outer circumference of the camshaft 1 respectively. 2 combs.

How best in 2 shown, each cam piece 5 two axially spaced cam groups 7 on. Each of the two cam groups 7 acts with a roller of a pivotally mounted roller finger follower of one of the two inlet and outlet valves of each cylinder and has three juxtaposed cams 8th . 9 . 10 on. The cams 8th . 9 . 10 each have different cam profiles and can be by axial displacement of the cam piece 5 on the camshaft 1 respectively. 2 in three corresponding displacement positions, either with the role of the rocker arm of the associated valve in abutting contact bring. The cam profiles of the three cams 8th . 9 . 10 can vary in height and / or in the circumferential direction of the camshaft 1 respectively. 2 have staggered vertices, so that the associated valve is opened or closed at different times and / or at different times, depending on which of the three cams 8th . 9 . 10 interacts with the role of the rocker arm. The order of the three cams 8th . 9 . 10 is with all cam groups 7 on the cam pieces 5 same, so the cam pieces 5 can be made as equal parts.

The two cam groups 7 each point to the cams 8th . 9 . 10 opposite, in 2 down and in 5 upwardly facing side of the cam piece 5 a base circle section 11 whose outer diameter over the entire axial length of the two cam groups 7 it is the same and extends over a circumferential angle of about 180 degrees. The axial displacement of the cam pieces 5 on the camshaft 1 respectively. 2 to adjust the stroke and / or the opening times of the associated valves is made if necessary and takes place whenever the base circle section 11 the two cam groups 7 during a rotation angle of the camshaft 1 respectively. 2 180 degrees from the roles of the drag lever opposite. The amount of axial displacement of the cam piece 5 between two adjacent displacement positions corresponds to the center distance of adjacent cams 8th . 9 respectively. 9 . 10 ,

So that the cam pieces 5 If necessary, it can be moved to any of the three displacement positions, for each cam piece 5 provided a worm drive. The worm drives each comprise a circumferential Y-shaped groove 12 that extends in the peripheral surface of an extended, to a frontal end 13 of the cam piece 5 adjacent section 14 of the cam piece 5 is recessed, and a stationary mounted in the cylinder head housing actuator (not shown) with three spaced axially spaced driving pins. One of the driving pins can be one each extend by actuation of the actuator and with its free end with the groove 12 engage the cam piece 5 each about the center distance between two adjacent cams 8th . 9 respectively. 9 . 10 in the axial direction of the camshaft 1 respectively. 2 to the sprocket 4 to move towards or away from this.

The training and operation of the worm gear and the actuators is mentioned in the introduction DE 10 2007 010 149 A1 the applicant described in detail.

To the cam pieces 5 in relation to the axis of rotation of the camshaft 1 respectively. 2 To center and keep them centered during their displacement with respect to the axis of rotation, is each of the cam pieces 5 by means of a radial bearing 15 rotatable in the upper part 3 stored the cylinder head housing. How best in the 3 . 4 and 9 represented, consist of radial bearings 15 from a designed as a sliding bearing piece 16 that is one between the two cam groups 7 arranged cylindrical section 17 the cam piece is mounted around. The outer diameter of the section 17 is smaller than the diameter of the base circle section 11 the two adjacent cam groups 7 and slides as the camshaft rotates 1 respectively. 2 with its outer peripheral surface 18 on the adjacent inner peripheral surface 19 of the bearing piece 16 ,

How best in 3 shown, there is each bearing piece 16 from two half-shells 20 . 21 , before mounting the cam piece 5 on the camshaft 1 respectively. 2 on the cylindrical section 17 of the cam piece 5 to the bearing piece 16 be assembled so that this in relation to the cam piece 5 axially immovable and together with the cam piece 5 on the camshaft 1 respectively. 2 is shifted when the cam piece 5 if necessary moved to another displacement position.

The advantages of one together with the cam piece 5 Sliding bearing are in the aforementioned DE 10 2007 010 148 A1 described in detail.

In the bearing piece shown in the drawing 16 become the opposite flat contact surfaces of the two half-shells 20 . 21 by elastic spring clips 22 pressed against each other, which the half-shells 20 . 21 on the cam piece 5 stick together. The spring clips 22 have a low mass and allow disassembly of the bearing pieces 16 , Alternatively it is but also possible, the two half shells 20 . 21 screw together or glue together, in the latter case expedient two previously by cracking of the bearing piece 16 produced half-shells 20 . 21 used to improve the accuracy of fit and the cohesion of the contact surfaces.

After mounting all bearing pieces 16 on the cam pieces 5 each four such pre-assembled cam pieces 5 with the same orientation one behind the other on the intake or exhaust camshaft 1 respectively. 2 deferred before this then together with the cam pieces 5 in the axial direction in a broken storage tunnel in the upper part 3 of the cylinder head housing are inserted. As in 1 each bearing tunnel consists of four transverse to the axis of rotation of the camshaft 1 respectively. 2 aligned tunnel sections 23 in the axial direction of the camshaft 1 respectively. 2 in each case between two valves of a cylinder in one piece on the upper part 3 are formed and a passage opening 24 in the radial direction on all sides limit, through which the bearing pieces 16 let it move axially with a sliding fit. When the camshafts 1 . 2 are completely inserted into the storage tunnel, serves each passage opening 24 as a seat for one of the bearing pieces 16 , These are after the assembly of the camshafts 1 . 2 in the upper part 3 in each associated tunnel section 23 pinned, so they together with the cam pieces 5 are axially displaceable by a limited amount, but non-rotatably in the passage opening 24 be held.

For the pinning of the bearing pieces 16 serve cylindrical pins 25 that after inserting the camshaft 1 respectively. 2 in their tunnel bearings from the outside in cylindrical through holes in the tunnel sections 23 be inserted so that its inner end in an opposite, in the outer peripheral surface of the bearing piece 16 recessed axial groove 26 engages as best in 6 shown. The width of the grooves 26 is slightly larger than the diameter of the pins 25 so that the bearing piece 16 in the tunnel section 23 Although it can move axially, it can not rotate. The displacement of the bearing piece 16 becomes in both directions by a closed front end 27 from one of the two grooves 26 limited. As in 6 shown lies in the outer displacement positions of the cam piece 5 one each of these rounded ends 27 against the in the groove 26 engaging pen 25 at.

How best in 8th shown, shows each bearing piece 16 three obliquely downwardly facing, in the axial distance from each other arranged radial lubricant channels 28 on, extending from the outer peripheral surface of the bearing piece 16 through the lower half shell 21 through to its cylindrical inner peripheral surface 19 extend in sliding contact with the rotating peripheral surface 18 of the section 17 of the cam piece 5 stands. The axial distance between adjacent lubricant channels 28 corresponds to the center distance of adjacent cams 8th . 9 . 10 , so that in each of the three displacement positions of the cam piece 5 and thus the bearing piece 16 one of the lubricant channels 28 with a lubricant supply channel 29 communicates through the pressurized engine oil into the radial bearing 15 is supplied. To a leakage of the supplied engine oil through the two other lubricant channels 28 prevent the tunnel sections 23 in the area of lubricant channels 28 axial protrusions 30 ( 7 ) on which these lubricant channels 28 Close or mask radially from the outside.

The outer diameter of the bearing pieces 16 is greater than the circle diameter of the largest cam 9 so that the cam groups 7 if necessary, into the passage opening 24 of the tunnel section 23 let it move in. This allows the axial bearing width of each bearing piece 16 in the upper part 3 be made relatively large. In conjunction with the closure of the lubricant channels 28 through the projections 30 Nevertheless, an optimal lubricant supply is guaranteed.

To the cam pieces 5 to hold in the desired displacement position, is each of the bearing pieces 16 by means of two diametrically opposed locking devices 31 axially lockable in the three displacement positions. How best in 9 illustrated, includes each locking device 31 two above and below the camshafts 1 . 2 in a radial bore 32 in the tunnel section 23 radially displaceable detent balls 33 each of which is a preloaded helical compression spring 34 is pressed radially inward to them with an axial locking bar 35 on the adjacent top or bottom of the bearing piece 16 to engage in detention. The radial bore 32 is at the outer end by a screwed cap 36 closed, whereby the assembly of the detent balls 33 and the helical compression springs 34 after mounting the camshaft 1 respectively. 2 in the upper part 3 is simplified.

How best in 3 are shown, the locking strips 35 in diametrically opposed axial recesses 37 in the outer peripheral surface of the bearing piece 16 used and each have two at an axial distance from each other to the axis of rotation of the camshaft 1 respectively. 2 protruding mounting pins 38 on, with the interference fit in complementary holes of the half shells 20 . 21 of the bearing piece 16 are used. Alternatively, instead of the locking strips 35 also in the bearing piece 16 integrated Arretierkulissen be provided, which are milled out during processing and then cured.

Each locking bar 35 or Arretierkulisse has a central locking recess 39 on, on both sides by a projection 40 from an adjacent lateral flank 41 is disconnected. In the in 9 shown central displacement position of the cam piece 5 grips the detent ball 33 in the detent recess 39 one, while in the two outer displacement positions against one of the two flanks 41 is present, as in 10 shown. In the outer displacement positions presses of the spring-loaded detent ball 33 on the flank 41 the Arretierkulisse applied axial force the bearing piece 16 at the closed front end 27 the groove 26 against the stationary pen 25 to it against the top 3 to brace the cylinder head housing.

Further details on the design and operation of such a locking device with a detent recess and two flanks are not vorveröffentlichen DE 10 2007 010 150 A1 the applicant described in detail.

By providing two diametrically arranged locking devices 31 can the inclination of the cam pieces 5 be reduced to "tilting" during the move.

After inserting the pre-assembled camshaft 1 . 2 into the tunnel bearing of the upper part 3 of the cylinder head housing and after completion of the upper part 3 by inserting the locking balls 33 and helical compression springs 34 becomes the shell 3 with a already attached to the cylinder crankcase cylinder head base (not shown) screwed.

On the one hand, a sufficient width of the cams 8th . 9 . 10 the cam groups 7 each cam piece 5 on the other hand to ensure sufficient switching clearance, so that a contact between two adjacent, located in different outer displacement positions cam pieces 5 is avoided, with the Y-shaped groove 12 provided section 14 each cam piece 5 with an extended, to the axis of rotation of the camshaft 1 respectively. 2 coaxial recess 42 in the front end 13 provided, in which the opposite front end 43 of the adjacent cam piece 5 over a part of the length of the outermost end cam 8th can dip, as in 10 shown.

LIST OF REFERENCE NUMBERS

1

Camshaft, intake camshaft

2

Camshaft, exhaust camshaft

3

Upper part of the cylinder head housing

4

Sprocket

5

cam piece

6

internal gearing

7

cam group

8th

cam

9

cam

10

cam

11

Base circle portion

12

Y-shaped groove

13

Front end of the cam piece

14

extended section of the cam piece

15

radial bearings

16

stock items

17

cylindrical section

18

outer peripheral surface

19

inner peripheral surface

20

half shell

21

half shell

22

spring clip

23

Tunnel section, bracket

24

Through opening

25

pen

26

axial groove

27

front end

28

lubricant channels

29

Lubricant supply channel

30

head Start

31

locking device

32

radial bore

33

detent ball

34

Helical compression spring

35

locking strip

36

cap

37

recess

38

fastening pins

39

latching depression

40

projections

41

flanks

42

recess

43

Front end of the cam piece

Claims (16)

Valve train for gas exchange valves of an internal combustion engine with a camshaft ( 1 . 2 ), at least two rotationally fixed and axially displaceable on the camshaft ( 1 . 2 ) guided cam pieces ( 5 ) each with a radial bearing ( 15 ) for rotatably supporting the cam pieces ( 5 ) and the camshaft ( 1 . 2 ), as well as holders ( 23 ) for the radial bearings ( 15 ), in which the radial bearings ( 15 ) secured against rotation and are held axially displaceable, characterized in that the holders ( 23 ) in one piece with a top ( 3 ) are formed of a two-part cylinder head housing and as a seat for the two shells ( 20 . 21 ) existing radial bearings ( 15 ) serving through openings ( 24 ) in the radial direction on all sides, and that the radial bearings ( 15 ) have an outer diameter which is larger than the largest Circle diameter of cams ( 8th . 9 . 10 ) of the cam pieces ( 5 ). Valve gear according to claim 1, characterized in that the camshaft ( 1 . 2 ) with the cam pieces ( 5 ) and the radial bearings ( 15 ) through the passage openings ( 24 ) axially into the brackets ( 23 ) is inserted. Valve gear according to claim 2, characterized in that the radial bearings ( 15 ) in the holders ( 23 ) secured against rotation and together with the cam pieces ( 5 ) are axially displaceable between two end stops. Valve gear according to claim 3, characterized in that each holder ( 23 ) comprises at least one anti-rotation and / or stop element, which by the holder ( 23 ) into an axial groove ( 26 ) of the radial bearing ( 15 ) intervenes. Valve gear according to claim 4, characterized in that the anti-rotation and / or stop element in the radial direction from the outside through a bore of the holder ( 23 ) pin ( 25 ), whose inner front end in the axial groove ( 26 ) of the radial bearing ( 15 ) intervenes. Valve gear according to claim 1, characterized in that the two half-shells ( 20 . 21 ) by spring clips ( 22 ) are interconnected. Valve gear according to claim 1, characterized in that the two half-shells ( 20 . 21 ) are connected by screws. Valve gear according to claim 1, characterized in that the two half-shells ( 20 . 21 ) are glued together. Valve gear according to claim 8, characterized in that the two half-shells ( 20 . 21 ) by cracking the radial bearing ( 15 ) are made. Valve gear according to one of the preceding claims, characterized in that the cam pieces ( 5 ) two cam groups ( 7 ) with three different cams ( 8th . 9 . 10 ) and that the radial bearings ( 15 ) can be locked in three discrete displacement positions whose distance from the center distance of the cam ( 8th . 9 . 10 ) corresponds. Valve gear according to claim 10, characterized in that each cam piece ( 5 ) by at least one on the radial bearing ( 15 . 16 ) acting locking device ( 31 ) is lockable in the discrete shift positions. Valve gear according to claims 4 and 11, characterized in that the locking devices ( 31 ) the cam pieces ( 5 ) in opposite outermost displacement positions against the anti-rotation and / or stop element ( 25 ). Valve gear according to claim 11 or 12, characterized in that each cam piece ( 5 ) by two diametrically opposed locking devices ( 31 ) is lockable. Valve gear according to one of the preceding claims, characterized by a plurality of lubricant channels ( 28 ), each radial bearing ( 15 ) in the axial direction spaced apart, wherein in the radial direction outer junctions of a part of the lubricant channels ( 28 ) by a projection ( 30 ) of the associated holder ( 23 ) are closed. Valve gear according to one of the preceding claims, characterized in that at least a part of the cam pieces ( 5 ) one the camshaft ( 1 . 2 ) surrounding frontal recess ( 42 ), in which an opposite end ( 43 ) of an adjacent cam piece ( 5 ) is insertable. Internal combustion engine, characterized by at least one valve drive according to one of the preceding claims.

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