DE102007022145A1 - Reversible valve train of an internal combustion engine - Google Patents

Abstract

A reversible valve train (3) of an internal combustion engine (2) is proposed, comprising a drive shaft (6) and a cam piece (7) arranged in a rotationally fixed and axially displaceable manner on the drive shaft (6) and comprising a cam group (10 ) has adjacent cams (10a, 10b, 10c) with different cam lobes and is radially supported together with the drive shaft (6) at a camshaft bearing point (9). In this case, a radially between the camshaft bearing point (9) and the cam piece (7) arranged and together with the cam piece (7) axially displaceable bearing bush (19) may be provided which is secured against rotation relative to the camshaft bearing point (9) and with its inner circumferential surface (18 ) on the cam piece (7) adjacent to the cam group (10) extending around the bearing pin (17), wherein the inner lateral surface (18) has a bearing width which is greater than the bearing width of the camshaft bearing point (9).

Description

Field of the invention

The The invention relates to a switchable to different Gaswechselventilhübe Valve gear of an internal combustion engine, with a camshaft, the a drive shaft and at least one rotatably on the drive shaft and axially displaceably arranged cam piece comprising at least one Cam group of axially adjacent cams with different from each other Has cam lobes and together with the drive shaft a stationary in the internal combustion engine arranged camshaft bearing radially supported is, and with an actuator for axial displacement of the cam piece.

Background of the invention

Such a valve train is known in the art and is for example from the DE 101 48 179 A1 out. The valve train proposed therein has a drive shaft with an outer longitudinal toothing and a cam piece axially displaceable thereon with an inner longitudinal toothing corresponding to the outer longitudinal toothing and cam pairs arranged on both sides of a camshaft bearing bearing cam elevations different from one another. The actuator for axially displacing the cam piece comprises controllable actuator pins which cooperate with associated axial grooves formed on the cam piece such that the cam piece is displaced during the common base circle phase of the cam pairs on the cam follower element designed as a roller cam lever by switching over the respectively effective cam elevation.

Thereby, that on the cam piece trained bearing pin directly in the camshaft bearing slidably, the axial distance between the camshaft bearing point and of the camshaft bearing closest and currently effective cam be at least as large as the entire displacement of the cam piece. Under consideration a required minimum width of each cam forces this arrangement usually, however, to a significant width reduction of Camshaft bearing opposite usual, non-reversible valve trains and / or, as in the cited document executed to a restriction to a maximum of two cams per cam group. A related Disadvantage is on the one hand the increased wear risk the narrow camshaft bearing due to the unfavorable Conditions for the formation of a sufficiently viable hydrodynamic lubricant film in the plain bearing while the use of adapted to the life of the internal combustion engine roller bearing within the axial space supply of the camshaft bearing point readily unrealizable appears. The limited number the cam per cam group leads on the other hand that an improvement in the performance, fuel consumption and and exhaust emission behavior of the internal combustion engine by adjusting the Gaswechselventilhübe to the different operating ranges of the internal combustion engine only possible within narrow limits is.

Object of the invention

Of the Invention is therefore the object of a valve train of the aforementioned type so that the disadvantages indicated be avoided by simple means. Accordingly, should simultaneously a sufficiently stable and life-long radial support the Camshaft created in the camshaft bearing and at the same time a increased flexibility in terms of the number of cams per cam group and / or the respective cam widths possible become. The valve train should also in a simple way and under High-volume conditions economical be produced.

Summary of the invention

The solution This object is apparent from the features of claim 1, while advantageous Further developments and embodiments of the dependent claims are. Accordingly, the object is achieved in that a radially between the Camshaft bearing and the cam piece arranged and together axially displaceable with the cam piece Bearing bush is provided. The bearing bush is against twisting across from the camshaft bearing secured and surrounds with its inner circumferential surface a adjacent to the cam piece to the cam group extending bearing pin, wherein the inner circumferential surface a Has bearing width greater than the bearing width of the camshaft bearing is.

Due to the radial interposition of the rotating stationary bearing bush between the camshaft bearing and the bearing pin of the cam piece, the storage function of the camshaft bearing point can be reduced to a quasi-static, that is free of relative component rotation and consequently narrow-built support. The resulting from the cited prior art axial space surplus can be used in favor of a higher number of cams per cam group and / or in favor of increased cam widths. Due to the axially co-moving with the cam bearing bush, the bearing width of the bearing pin encompassing inner lateral surface of the bearing bush at the same time compared to that in the cited State of the art disclosed arrangement in favor of a lifetime durability of a sliding or rolling bearing can be significantly increased.

unscathed the fact that the camshaft bearing now clear schmalbauender be performed as the inner circumferential surface of the bearing bush can, and that the bearing bushing relative to the camshaft bearing point moved axially, It is provided in development of the invention that the storage of the journal in the bushing as from the lubricant circuit formed of the internal combustion engine supplied, hydrodynamic sliding bearing is. A targeted and undesirable lubricant leakage free supply of the plain bearing can open in the direction of its check valves done in on the outer circumference of the Bushing axially spaced recesses extend and whose number is identical to the number of cams per cam group is. The sliding bearing is dependent on the axial position of the cam piece across from the camshaft bearing over one each of the check valves to a lubricant supply channel opening into the camshaft bearing connected.

A Such hydraulic circuit for supplying lubricant to the Slide bearing can also be designed to be particularly simple and effective, that the Bearing bush a parallel to the longitudinal axis extending distribution line having a central opening in the inner circumferential surface supply bore for the lubricant connects with the recesses.

As previously explained, it is also easy possible, provide three cams per cam group. While that of a cam group associated Cams independent from their number of different cam surveys in terms of Maximalhubs and / or the phase position, it can at a Boundary case of a cam lobe be provided that one of the cams as closest within the cam group arranged to camshaft bearing base cam for gas exchange valve shutdown is formed and upon axial displacement of the cam piece in the camshaft bearing dips in such a way that the camshaft bearing point and the base circle cam overlap axially. The gas exchange valve shutdown can be known either to improve the charge change and mixture formation or for complete shutdown single cylinder of the internal combustion engine can be used. simultaneously allows the immersion of the base circle cam in the camshaft bearing an axial extraordinarily compact design of the cam piece, which is a series connection of three or more cams per cam group much easier. As an alternative to the pure base cam but it can also be provided within the cam group next lying Cam arranged for camshaft bearing with a comparatively small cam lobe, which in case of sufficient radial space also available in the camshaft bearing dips.

In preferred development of the invention, it is provided that the cam piece has two arranged on both sides of the bearing bush cam groups. It is the expert in the field of such valve controls Of course aware that one for both groups of cams identically oriented order of different Cam elevations is to make the same stroke change arranged on both sides of the camshaft bearing gas exchange valves to achieve a cylinder.

• • zwei am Nockenstück ausgebildete Nockenbahnen mit in Längsrichtung der Nockenwelle wirksamen und einander zugewandten Hubprofilen mit über deren Umfang im wesentlichen konstantem Abstand;
• • eine zur Längsachse der Nockenwelle parallel angeordnete und gegen Verdrehen um die Längsachse der Nockenwelle gesicherte Stößelstange, deren Stirnflächen sich in Eingriff mit den Nockenbahnen befinden;
• • eine ansteuerbare Feststelleinrichtung zur form- und/oder reibschlüssigen Axialfixierung der Stößelstange.

While the cam piece with the bearing bush as an essential part of the invention can also be combined with the actuating devices known from the prior art for the axial displacement of the cam piece, the invention also makes it possible to use an actuating device having the following features:

• • two cam tracks formed on the cam piece with stroke profiles that are effective in the longitudinal direction of the camshaft and facing each other with a substantially constant distance over their circumference;
• • a push rod which is arranged parallel to the longitudinal axis of the camshaft and secured against rotation about the longitudinal axis of the camshaft, the end faces of which are in engagement with the cam tracks;
• • a controllable locking device for positive and / or frictional axial fixation of the push rod.

With Such an actuator, whose How it works in detail is explained in the context of the description of an embodiment, can also be in favor of the number of cams per cam group and / or the respective cam width axially extremely compact cam piece shown become.

This is especially true when the cam piece in cross-section annular and facing longitudinal recesses, which extend radially within the arranged on both sides of the bearing bush cam groups and at the bottoms of the cam tracks are formed. As a result, the radial space between the drive shaft and the common cam all cam group base circle diameter for accommodating the axial position of the cam piece controlling Stö be used barel.

A through the longitudinal recesses unavoidable weakening the radial design strength of the cam piece may, if necessary be compensated in that the bearing bush stepped radially inward Having end portions which extend into the longitudinal recesses. As a result, the cams which extend above the longitudinal recesses, sufficiently supported the bearing bush.

While the longitudinal the camshaft effective Hubprofile the cam tracks in principle can have any axial profile and only one Moving the cam piece outside the cam common Grundkreisphase is excluded, is it in favor of a speedy one and defined axial displacement of the cam piece particularly useful when each of the lifting profiles consists of a rising flank, a sloping one Flank and composed between the flanks Rastbahnen composed is.

to Reduction of friction between the end faces of the push rod and the cam tracks It is further contemplated that the push rod formed both ends Socket has, wherein the end faces rotatable in the joint sockets mounted balls are formed. In this case, the cam tracks in favor reduced contact pressures and reduced contact wear a to the balls substantially complementary profile in longitudinal section exhibit.

Furthermore the bushing can be advantageous for guiding purposes of the push rod be used by the pushrod in one or more longitudinal bores aligned with each other through the bearing bush longitudinally movable is stored.

• • ein längliches, orthogonal zur Nockenwelle ausgerichtetes Gehäuse mit einer ersten Längsbohrung, einer sich an die erste Längsbohrung anschließenden zweiten Längsbohrung und einer quer im Gehäuse verlaufenden Durchführung für die Stößelstange, in welcher Durchführung die zweite Längsbohrung mündet;
• • das Piezostapelelement ist in der ersten Längsbohrung angeordnet und an einem in der ersten Längsbohrung eingesetzten Verschlussstopfen axial abgestützt;
• • der Schieber ist in der zweiten Längsbohrung längsbeweglich gelagert und erstreckt sich bis zur Durchführung, die eine gegenüber dem Schieber verlaufende Klemmfläche aufweist.

In a preferred embodiment, the locking device is intended to have an electrically energizable piezo stacking element and a slide actuated therefrom and directed onto the outer circumferential surface of the pushrod, which fixes the pushrod axially by clamping when the piezo stacking element is energized. Due to the high precision, extremely fast and with high actuation force expanding piezoelectric element under energization, a reproducible switching operation of the cam piece can be performed even at high speeds of the internal combustion engine by timely precise and sufficiently non-slip clamping of the push rod. The locking device should have the following features in a specific embodiment:

• • An elongate, orthogonal to the camshaft aligned housing having a first longitudinal bore, a subsequent to the first longitudinal bore second longitudinal bore and a transversely extending in the housing passage for the push rod, in which implementation the second longitudinal bore opens;
• The piezo stacking element is arranged in the first longitudinal bore and axially supported on a sealing plug inserted in the first longitudinal bore;
• • The slide is longitudinally movably mounted in the second longitudinal bore and extends to the implementation, which has a clamping surface extending relative to the slider.

The for the Durability of a piezo stack element usually required Spring preload can easily with a provision the slide are connected by the slide in longitudinal section T-shaped with a cylindrical, facing the piezo stacking element and a Hubübertragungsfläche having headpiece and with one of the head piece outgoing and in the second longitudinal bore extending cylindrical bolt is formed, wherein between one of the Hubübertragungsfläche opposite annular end face of the headpiece and the bottom of the first longitudinal bore a compression spring means is clamped.

The functionality in the case to a unit summarized locking device can continue to be advantageously extended by the fact that in the locking device an Axialrastiereinrichtung for the bearing bush is integrated. Here is the Axialrastiereinrichtung in one in the housing extending third longitudinal bore with opening directed to the bearing bush and disposed with a bottom and has a spring-supported compression spring means and one in the area of the opening extending, from the compression spring means optionally with interposition a pressure piece recording force-loaded pressure piece on. This acts with one of each locking contours, which on the outer circumference the bearing bush axially spaced, form-fitting together. With such a Axialrastiereinrichtung is on the one hand a defined Axial position of the cam piece across from the gas exchange valve actuated Nockenabgriffselement ensured and on the other hand, an uncontrolled Moving the cam piece prevented.

A further functional integration of the locking device is obtained when the Axialrastiereinrichtung also serves to prevent rotation of the bearing bush relative to the camshaft bearing by the pressure piece, the locking contours and a respective extending between the locking contours Ü transition contour in cross section are substantially flat. As a result, the functionally relevant rotation of the bearing bush is not only in the individual axial positions of the cam piece, but also in the intermediate transition positions sufficiently effective.

Around with the speed of the internal combustion engine and consequently with the Switching dynamics of the cam piece increasing demands for low inertia and at the same time highest wear resistance can meet the claimed during the switching contact surfaces, can the bearing bush finally have an insert on which insert the locking contours extend. In this case, the bearing bush made of a lightweight material, preferably Aluminum and the insert made of a steel material with hardened surface be.

Brief description of the drawings

Further Features of the invention will become apparent from the following description and from the drawings, in which an embodiment of the valve gear according to the invention partially simplified or shown schematically. These are functionally identical Features or components provided with the same reference numbers. Show it:

1 a perspective view of a valve gear according to the invention in the mounted state in the internal combustion engine;

2 a perspective view of a longitudinal section through the valve train according to 1 ;

3 a perspective view of a longitudinal section through the cam piece according to 2 ;

4 a perspective view of the section of the internal combustion engine according to 1 ;

5 a schematic representation of the lubricant supply arranged in the bearing bush and the journal of the cam piece overlapping slide bearing;

6 a perspective view of the bearing bush according to 2 with view of the recesses for the check valves according to 5 ;

7 a perspective view of the bearing bush according to 2 with view of an insert mounted thereon;

8th a perspective view of the bearing bush according to 7 without the insert part;

9 a perspective view of the insert according to 7 ;

10 a perspective view of a longitudinal section through a locking device according to 1 ;

11 a perspective view of a push rod according to 2 ;

12 Schematic representations of the operation of an actuator according to the invention for the axial displacement of the cam piece from a first to the second end position and

13 the schematic representations analogous to 12 in the axial displacement of the cam piece from the second to the first end position.

Full Description of the drawings

In 1 is an inventive, in a cylinder head 1 an internal combustion engine 2 mounted valve train 3 in cutting for a cylinder of the internal combustion engine 2 disclosed. Shown is a camshaft 4 with an external longitudinal toothing 5 having drive shaft 6 and with a cam piece 7 , with one to the external longitudinal teeth 5 corresponding inner longitudinal toothing 8th rotatably and axially displaceable on the drive shaft 6 is arranged. The cam piece 7 has both sides of a stationary in the internal combustion engine 2 arranged and the camshaft 4 radially supporting camshaft bearing 9 arranged cam groups 10 and 11 on, each consisting of three axially adjacent cams 10a . 10b and 10c respectively. 11a . 11b and 11c are composed of mutually different cam lobes and identical base circle diameter. The cams 10a and 11a are designed as lift-free Grundkreisnocken.

Depending on the instantaneous axial position of the cam piece 7 transferred on both sides of the camshaft bearing 9 arranged cam follower 12 , here as each on a support element 13 pivotally mounted roller rocker arms are formed, the hub of the respectively engaged with these cam 10a . 10b or 10c respectively. 11a . 11b or 11c on gas exchange valves 14 , In the illustrated axial position of the cam piece 7 are each the base circle cam 10a and 11a active, so that the gas exchange valves concerned 14 completely shut down.

An electrically controllable locking device 15 , rigidly on the cylinder head 1 attached and orthogonal to the camshaft 4 is aligned, serves as part of an actuator 16 both for axial displacement and for axial locking of the cam piece 7 in its respective axial position. A closer explanation of the actuator 16 will be done later with appropriate illustrations.

A better understanding of the structure of the camshaft bearing 9 mounted camshaft 4 results from the sectional view according to 2 , The cam piece 7 has one between the cam groups 10 and 11 extending trunnion 17 on that in an inner surface 18 one from the camshaft bearing 9 radially supported and with low axial clearance together with the cam piece 7 axially displaceable bearing bush 19 sliding bearing rotates. As explained later, the bushing is 19 against twisting against the camshaft bearing 9 secured. It can be clearly seen that the bearing width of the inner circumferential surface 18 the bearing bush 19 in favor of a sufficiently viable lubricating film in the hydrodynamic plain bearing 20 significantly wider than the bearing width of the camshaft bearing 9 can be executed, in which the bearing bush 19 only moved axially. Sufficient radial support of the camshaft 4 can still be guaranteed if the within the cam group 10 next to the camshaft bearing 9 arranged base circle cams 10a into the camshaft bearing 9 dips, so that the camshaft bearing point 9 and the base circle cam 10a overlap axially.

In the context of here below the camshaft bearing point 9 to the cylinder head 1 bolted locking device 15 are also two on the cam piece 7 trained cam tracks 21 and 22 and a pushrod 23 as elements of the actuator 16 significant. The cam tracks 21 . 22 point in the longitudinal direction of the camshaft 4 effective Hubprofile, which are facing each other over the circumference thereof at a substantially constant distance and in engagement with end faces 24 to the longitudinal axis of the camshaft 4 arranged in parallel and against rotation about the longitudinal axis of the camshaft 4 secured pushrod 23 are located. An axially particularly compact design of the cam piece 7 is thereby made possible that the cam piece 7 in cross-section annular and facing longitudinal recesses 25 which is radially inward of the cam groups 10 . 11 run and at their bottoms 26 the cam tracks 21 . 22 are formed. In this case, an impermissibly high radial deflection of the two cam groups under load 10 . 11 This prevents the bearing bush 19 radially inwardly stepped end portions 27 has, extending in the longitudinal recesses 25 extend and radial support of the cam 10a and 11c serve. By this measure, the bearing width of the inner shell surface is at the same time 18 around the width of both end sections 27 elevated. The low axial clearance between the cam piece 7 and the axial mitbewegten bearing bush 19 turns in this case as the difference of the face distance of the cams 10a and 11c and the shoulder spacing of the end portions 27 represents.

One way of manufacturing and assembling the in 3 shown cam piece 7 consists of one or both cam groups 10 . 11 separately from an inner tube section, on which the inner longitudinal toothing 8th and the journal 17 run, and together with the bearing bush 19 and the longitudinally movably guided push rod 23 to assemble to a unit. The cam groups can 10 . 11 each manufactured as a one-piece component or else from separately produced and mounted on the inner tube section cams 10a . 10b . 10c respectively. 11a . 11b . 11c be composed. The on the floors 26 the longitudinal recesses 25 extending cam tracks 21 . 22 If necessary, they can also be manufactured separately and in the longitudinal recesses 25 be formed firmly inserted rings. Such rings can be like the cam groups 10 . 11 or the individual cams 10a . 10b . 10c respectively. 11a . 11b . 11c For example, be prepared in sintered, extruded or Metallspritzgießverfahren. The attachment of the cam group or groups of cams 10 . 11 and if necessary. the cam tracks 21 . 22 on the inner pipe section or in the longitudinal recesses 25 can be done by expert force, form or cohesive bonding techniques.

From the representation of the cylinder head 1 in 4 on the one hand go one side in the cylinder head 1 attached receiving opening 28 as well as bolting points 29 for the locking device 15 out. On the other hand, one is in the lower half shell 30 the camshaft bearing 9 opening supply channel 31 recognizable for lubricant, that of the lubricant circuit of the internal combustion engine 2 branches off and to supply the sliding bearing 20 between the journal 17 of the cam piece 7 and the inner circumferential surface 18 the bearing bush 19 serves. A detailed view of the sliding bearing 20 with the lower half shell 30 , the supply channel 31 , the bearing bush 19 and the journal 17 goes out schematically 5 out. A sufficient lubricant supply of the sliding bearing 20 is despite the comparatively narrow bearing width of the camshaft bearing 9 in all axial positions of the bearing bush 19 without free lubricant outlet from the supply channel 31 thereby ensuring that on the outer circumference of the bearing bush 19 axially spaced recesses 32 with check valves arranged therein 33 run in the direction of the sliding bearing 20 to open. Consequently, the lubricant is position-dependent on a respectively then open check valve 33 by first a parallel to the longitudinal axis of the bearing bush 19 extending distribution line 34 and then via a central in the inner circumferential surface 18 opening supply bore 35 in the plain bearing 20 promoted. Here are the others ande two check valves 33 closed and prevent free lubricant leakage from the supply channel 31 into the environment of the sliding bearing 20 ,

A view of the recesses 32 , their number with the number of cams per cam group 10 . 11 and hence the number of axial positions of the cam piece 7 is identical, as well as on the inner surface 18 the bearing bush 19 comes from 6 out. Clearly visible here are also through the end sections 27 running and aligned longitudinal bores 36 in which the pushrod 23 ( 2 ) is mounted longitudinally movable.

As it is from the 7 to 9 it can be seen has the bearing bush 19 an insert 37 on top of the recesses 32 opposite side on the outer circumference of the bearing bush 19 is attached. While the bearing bush 19 made of a lightweight material for the purpose of low mass effect when moving the cam piece 7 and preferably made of aluminum in favor of good sliding bearing properties at the same time, it is in the insert part 37 to a manufactured from steel material component with hardened surface, on the axially spaced latching contours 38 run. These act positively with a Axialrastiereinrichtung 39 for the bearing bush 19 together, as explained below.

The Axialrastiereinrichtung 39 is in the already off 1 known locking device 15 integrated, whose construction is closer from the in 10 shown longitudinal section emerges. The locking device 15 has an elongated housing 40 with a first longitudinal bore 41 on, in which an electrically energizable piezo stacking element 42 arranged and one end of one in the first longitudinal bore 41 inserted stopper 43 is axially supported. Expands under energization, actuates the piezo stack element 42 a slider 44 which is in a way to the first longitudinal bore 41 subsequent second longitudinal bore 45 smaller diameter is mounted longitudinally movable and, as will be explained later, the movement of the push rod 23 controls. For sealing the housing 40 opposite the receiving opening 28 in the cylinder head 1 ( 4 ) is used on the circumference of the housing 40 extending sealing ring 46 ,

The with the locking contours 38 of the insert part 37 according to 9 cooperating Axialrastiereinrichtung 39 is in a case 40 extending third longitudinal bore 47 with to the bearing bush 19 directed opening and with a floor 48 arranged and has one on the ground 48 supported compression spring means 49 , here in the form of two helical compression springs, and one of these kraftbeaufschlagtes pressure piece 50 and an intermediate and in the third longitudinal bore 47 longitudinally movably guided pressure piece receptacle 51 on. Both the pressure piece 50 as well as those on the insert 37 extending latching contours 38 as well as between the locking contours 38 running transition contours 52 are substantially flat in cross section, so that the interaction of the pressure piece 50 with the insert 37 not just an uncontrolled movement of the cam piece 7 from its respective axial position, but also the rotation of the bearing bush 19 opposite the camshaft bearing 9 causes.

The slider 44 is in longitudinal section T-shaped with a piezo stacking element 42 facing and a Hubübertragungsfläche 53 having cylindrical head piece 54 and with one of the head piece 54 outgoing and in the second longitudinal bore 45 extending cylindrical bolt 55 educated. A trained here as a disc spring package compression spring means 56 that is between one of the Hubübertragungsfläche 53 opposite annular end face 57 of the head piece 54 and the reason 58 the first longitudinal bore 41 is clamped, holds the slider 44 in permanent contact with the piezo stacking element 42 , The slider 44 extends up to one in the housing 40 running implementation 59 for the in 11 enlarged illustrated push rod 23 , whose outer circumferential surface 60 with energized piezo stacking element 42 and thus stroke-loaded slider 44 between an end face 61 of the cylindrical bolt 55 and one in the implementation 59 opposite clamping surface 62 during the switching of the cam piece 7 is axially fixed by friction. As an alternative to the cylindrical outer surface 60 the push rod 23 Of course, clamping surfaces with less or no curvature can be provided in favor of low contact pressures.

The following is the switching operation of the cam piece 7 including the schematic representations according to the 12 and 13 explained. In 12 are first of the cam groups 10 . 11 generated Gaswechselventilhübe 63a . 63b and 63c applied over the camshaft angle. At the Gaswechselventilhub 63a it is the zero stroke of the Grundkreisnocken 10a . 11a , Switching the cam piece 7 in the next axial position can be known only in the cam 10b . 11b . 10c . 11c common and extending here about 180 ° camshaft angle extending base circle phase, since a switching of the cam piece 7 be excluded in the phase of open gas exchange valves. In the 12 dotted curve symbolizes the course of the cam piece 7 trained cam tracks 21 . 22 according to the 2 and 3 with their in the longitudinal direction of the camshaft 4 effective stroke Profiles as unwinding over the camshaft angle. Each of the lifting profiles consists of a rising flank 64 , a falling edge 65 and between the flanks 64 . 65 running detent tracks 66 composed. Engage with the cam tracks 21 . 22 located push rod 23 can during the changeover operation of the internal combustion engine 2 oscillates axially freely and performs during each cam shaft rotation on the rising edges 64 corresponding axial stroke in the drawn plus direction and the falling edges 65 corresponding axial stroke against the plus direction.

As it is in the 12a - 12c is shown, there is a successive switching from the right in the figures to the left axial position of the cam piece 7 by timed operation of the locking device 15 and consequently by clocked clamping of the push rod 23 during the rising in positive direction flanks 64 , This clamping phase is in 12 illustrated by the solid line and leads to an axial repulsion of the cam piece 7 opposite to the then in the internal combustion engine 2 held stationary push rod 23 in the next axial position.

As explained above, serves also drawn Axialrastiereinrichtung 39 both the secure holding of the cam piece 7 in its individual axial positions as well as the permanent rotation of the bearing bush 19 , In the 12b illustrated starting position for a further switching operation of the cam piece 7 is reached after a full camshaft rotation after the push rod 23 during the flanks falling in the plus direction 65 unclamped from right to left has been traced. Because the pushrod 23 on the between the flanks 64 . 65 running detent tracks 66 ideally located at rest, the on and off times for the actuation of the locking device 15 easily on the currently engaged Rastbahnen 66 be placed. The reached after another switching operation axial position of the cam piece 7 according to 12c is identical to the one in 13a illustrated initial state for the switching takes place in the opposite direction from left to right cam piece 7 in its axial positions according to the 13b and 13c ,

The switching back takes place in analogous manner to the previous versions by axial repulsion of the cam piece 7 at the clocked clamped push rod 23 , How out 13 it can be seen, the clamping of the push rod takes place 23 but not on the rising flanks 64 but on the sloping flanks 65 so that the pushrod 23 during the rising flanks 64 each unrestrained from left to right is returned.

As in the 2 and 11 shown are the end faces 24 the push rod 23 through bullets 67 formed in both ends of the push rod 23 molded joint pans 68 are rotatably mounted. As a result, the between the end faces 24 and the cam tracks 21 . 22 occurring contact friction against a rigid in itself push rod significantly reduced. As it is also in the 2 and 3 can be seen simultaneously wear-promoting contact pressures between the balls 67 and the cam tracks 21 . 22 be reduced by the fact that the cam tracks 21 . 22 in longitudinal section one to the balls 67 have substantially complementary profile. In this context it should also be noted that under the claimed feature, according to which the facing Hubprofile the cam tracks 21 . 22 one should have over the circumference substantially constant distance, strictly speaking, not the geometric, but rather on the push rod 23 related distance to understand. As referenced distance is that axial distance between the cam tracks 21 . 22 referred to, taking into account the on the flanks 64 . 65 emigrating contact points of the faces 24 the push rod 23 to one over the circumference of the cam tracks 21 . 22 constant axial play of the push rod 23 leads.

1

cylinder head

2

Internal combustion engine

3

valve train

4

camshaft

5

External spline

6

drive shaft

7

cam piece

8th

Internal spline

9

Camshaft bearing

10

cam group

10a-c

cam

11

cam group

11a-c

cam

12

cam follower

13

supporting

14

Gas exchange valve

15

Locking device

16

actuator

17

pivot

18

Inner surface area

19

bearing bush

20

bearings

21

cam track

22

cam track

23

pushrod

24

face

25

longitudinal recess

26

ground the longitudinal recess

27

end

28

receiving opening

29

screw fixing

30

lower Half shell of the camshaft bearing

31

supply channel

32

recess

33

check valve

34

distribution line

35

supply hole

36

longitudinal bore for the pushrod

37

insert

38

catch contour

39

Axialrastiereinrichtung

40

casing

41

first longitudinal bore

42

Piezo stack element

43

sealing plug

44

pusher

45

second longitudinal bore

46

seal

47

third longitudinal bore

48

ground the third longitudinal bore

49

Spring means

50

Pressure piece

51

Pressure piece holder

52

Transition contour

53

Hubübertragungsfläche

54

Headpiece of the slider

55

cylindrical bolt

56

Spring means

57

Annular face

58

reason the first longitudinal bore

59

execution

60

Outer surface of the pushrod

61

Face of the cylindrical bolt

62

clamping surface

63a-c

Gaswechselventilhub

64

rising flank

65

falling flank

66

detent track

67

Bullet

68

socket

Claims (20)

To different Gaswechselventilhübe ( 63a . 63b . 63c ) reversible valve train ( 3 ) an internal combustion engine ( 2 ), with a camshaft ( 4 ), which has a drive shaft ( 6 ) and at least one on the drive shaft ( 6 ) rotatably and axially displaceable cam piece ( 7 ) comprising at least one cam group ( 10 ) axially adjacent cams ( 10a . 10b . 10c ) having mutually different cam lobes and together with the drive shaft ( 6 ) at a stationary in the internal combustion engine ( 2 ) arranged camshaft bearing point ( 9 ) is radially supported, and with an actuating device ( 16 ) for axially displacing the cam piece ( 7 ), characterized in that a radially between the camshaft bearing ( 9 ) and the cam piece ( 7 ) and together with the cam piece ( 7 ) axially displaceable bearing bush ( 19 ), which bearing bush ( 19 ) against rotation relative to the camshaft bearing ( 9 ) is secured and with its inner circumferential surface ( 18 ) one on the cam piece ( 7 ) adjacent to the cam group ( 10 ) extending trunnions ( 17 ), wherein the inner lateral surface ( 18 ) has a bearing width which is greater than the bearing width of the camshaft bearing point ( 9 ). Valve gear according to claim 1, characterized in that the bearing of the bearing journal ( 17 ) in the bearing bush ( 19 ) as from the lubricating telkreislauf the internal combustion engine ( 2 ) supplied hydrodynamic sliding bearing ( 20 ) is trained. Valve gear according to claim 2, characterized in that the supply of the sliding bearing ( 20 ) via in the direction of opening check valves ( 33 ) located in the outer circumference of the bearing bush ( 19 ) axially spaced recesses ( 32 ) and their number with the number of cams ( 10a . 10b . 10c ) per cam group ( 10 ) is identical, wherein the plain bearing ( 20 ) depending on the axial position of the cam piece ( 7 ) relative to the camshaft bearing ( 9 ) via in each case one of the check valves ( 33 ) to one in the camshaft bearing ( 9 ) opening supply channel ( 31 ) is connected for the lubricant. Valve gear according to claim 3, characterized in that the bearing bush ( 19 ) a parallel to the longitudinal axis extending distribution line ( 34 ) having a central in the inner circumferential surface ( 18 ) supply well ( 35 ) for the lubricant with the recesses ( 32 ) connects. Valve gear according to claim 1, characterized in that three cams ( 10a . 10b . 10c ) per cam group ( 10 ) are provided. Valve gear according to claim 1, characterized in that one of the cams ( 10a . 10b . 10c ) than within the cam group ( 10 ) next to the camshaft bearing point ( 9 ) arranged base cam ( 10a ) is formed for Gaswechselventilestilllegung, which Grundkreisnocken ( 10a ) with axial displacement of the cam piece ( 7 ) into the camshaft bearing ( 9 ) dips in such a way that the camshaft bearing ( 9 ) and the base cam ( 10a ) overlap axially. Valve gear according to claim 1, characterized in that the cam piece ( 7 ) two on both sides of the bearing bush ( 19 ) arranged cam groups ( 10 . 11 ) having. Valve gear according to claim 1, characterized in that the actuating device ( 16 ) for axially displacing the cam piece ( 7 ) has the following features: • two on the cam piece ( 7 ) formed cam tracks ( 21 . 22 ) in the longitudinal direction of the camshaft ( 4 ) effective and facing Hubprofilen with over its circumference at a substantially constant distance; • one to the longitudinal axis of the camshaft ( 4 ) arranged in parallel and against rotation about the longitudinal axis of the camshaft ( 4 ) secured push rod ( 23 ) whose end faces ( 24 ) engage with the cam tracks ( 21 . 22 ) are located; • a controllable locking device ( 15 ) for the positive and / or frictional axial fixation of the push rod ( 23 ). Valve gear according to claims 7 and 8, characterized in that the cam piece ( 7 ) in cross-section annular and facing longitudinal recesses ( 25 ) radially inwardly of the cam groups ( 10 . 11 ) and at their bottoms ( 26 ) the cam tracks ( 21 . 22 ) are formed. Valve gear according to claim 9, characterized in that the bearing bush ( 19 ) radially inwardly stepped end portions ( 27 ), which extend into the longitudinal recesses ( 25 ). Valve gear according to claim 8, characterized in that each of the lifting profiles from a rising edge ( 64 ), a falling edge ( 65 ) and between the flanks ( 64 . 65 ) extending detent tracks ( 66 ) is composed. Valve gear according to claim 8, characterized in that the push rod ( 23 ) at both ends molded sockets ( 68 ), wherein the end faces ( 24 ) through in the joint pans ( 68 ) rotatably mounted balls ( 67 ) are formed. Valve gear according to claim 12, characterized in that the cam tracks ( 21 . 22 ) in longitudinal section one to the balls ( 67 ) have substantially complementary profile. Valve gear according to claim 8, characterized in that the push rod ( 23 ) in one or more longitudinal bores ( 36 ) through the bearing bush ( 19 ) is mounted longitudinally movable. Valve gear according to claim 8, characterized in that the locking device ( 15 ) an electrically energizable piezo stacking element ( 42 ) and one from the piezo stacking element ( 42 ) and on the outer circumferential surface ( 60 ) of the push rod ( 23 ) directed slides ( 44 ), which the push rod ( 23 ) with energized piezo stacking element ( 42 ) fixed axially by clamping. Valve gear according to claim 15, characterized in that the locking device ( 15 ) has the following features: an elongated, orthogonal to the camshaft 4 ) aligned housing ( 40 ) with a first longitudinal bore ( 41 ), one to the first longitudinal bore ( 41 ) subsequent second longitudinal bore ( 45 ) and a transversely in the housing ( 40 ) ( 59 ) for the push rod ( 23 ), in which implementation ( 59 ) the second longitudinal bore ( 45 ) opens; The piezo stack element ( 42 ) is in the first longitudinal bore ( 41 ) and at one in the first longitudinal bore ( 41 ) inserted stopper ( 43 ) axially supported; • the slider ( 44 ) is in the second longitudinal bore ( 45 ) is longitudinally movable and extends to the implementation ( 59 ), one opposite the slider ( 44 ) extending clamping surface ( 62 ) having. Valve gear according to claim 16, characterized in that the slide ( 44 ) in longitudinal section T-shaped with a cylindrical, the piezo stack element ( 42 ) and a Hubübertragungsfläche ( 53 ) having head piece ( 54 ) and with one of the head piece ( 54 ) outgoing and in the second longitudinal bore ( 45 ) extending cylindrical bolt ( 55 ) is formed, wherein between one of the Hubübertragungsfläche ( 53 ) opposite annular end face ( 57 ) of the header ( 54 ) and the reason ( 58 ) of the first longitudinal bore ( 41 ) a compression spring means ( 56 ) is clamped. Valve gear according to claim 16, characterized in that in the locking device ( 15 ) an axial locking device ( 39 ) for the bearing bush ( 19 ), which Axialrastiereinrichtung ( 39 ) in a housing ( 40 ) extending third longitudinal bore ( 47 ) with to the bearing bush ( 19 ) directed opening and with a bottom ( 48 ) and one on the ground ( 48 ) supported compression spring means ( 49 ) and extending in the region of the opening, from the compression spring means ( 49 ) optionally with the interposition of a pressure piece receptacle ( 51 ) force-loaded pressure piece ( 50 ), which in each case one of latching contours ( 38 ) located on the outer circumference of the bearing bush ( 19 ) axially spaced, positively cooperates. Valve gear according to claim 18, characterized in that the Axialrastiereinrichtung ( 39 ) also as anti-rotation device for the bearing bush ( 19 ) relative to the camshaft bearing ( 9 ) serves by the pressure piece ( 50 ), the locking contours ( 38 ) and one each between the locking contours ( 38 ) transitional contour ( 52 ) are formed substantially flat in cross-section. Valve gear according to claim 18, characterized in that the bearing bush ( 19 ) an insert part ( 37 ) on which insert part ( 37 ) the locking contours ( 38 ), wherein the bearing bush ( 19 ) of a lightweight material, preferably aluminum and the insert part ( 37 ) are made of a steel material with a hardened surface.